<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019c4eb7-80da-7b03-b314-acf3695915f1,g:0f99ecd4-f332-48b6-9ae2-9929ec252db7-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.aosmith.com/role/CoverPage" xlink:type="simple" xlink:href="aos-20260331.xsd#CoverPage"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/CoverPage" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_019c4eb7-81a7-7eff-93b1-d9d5500828bb" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_DocumentInformationTable_019c4eb7-81a7-7eff-93b1-d9d5500828bb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019c4eb7-81a7-7c8c-b7df-2af63b2e651e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_019c4eb7-81a7-7eff-93b1-d9d5500828bb" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019c4eb7-81a7-7c8c-b7df-2af63b2e651e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c4eb7-81a7-7c8c-b7df-2af63b2e651e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c4eb7-81a7-7c8c-b7df-2af63b2e651e" xlink:to="loc_us-gaap_ClassOfStockDomain_019c4eb7-81a7-7c8c-b7df-2af63b2e651e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c4eb7-81a7-7225-9ae9-d5159fb9bea8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c4eb7-81a7-7c8c-b7df-2af63b2e651e" xlink:to="loc_us-gaap_ClassOfStockDomain_019c4eb7-81a7-7225-9ae9-d5159fb9bea8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019c4eb7-81a7-71d6-ac84-27d3ca9729bb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c4eb7-81a7-7225-9ae9-d5159fb9bea8" xlink:to="loc_us-gaap_CommonClassAMember_019c4eb7-81a7-71d6-ac84-27d3ca9729bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_CommonStockClassUndefinedMember_019c4eb7-81a7-76fd-8c15-600f79a744cf" xlink:href="aos-20260331.xsd#aos_CommonStockClassUndefinedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c4eb7-81a7-7225-9ae9-d5159fb9bea8" xlink:to="loc_aos_CommonStockClassUndefinedMember_019c4eb7-81a7-76fd-8c15-600f79a744cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019c4eb7-81a7-7c30-831b-ab40541331b5" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_DocumentType_019c4eb7-81a7-7c30-831b-ab40541331b5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_019c4eb7-81a7-7cc2-aac8-2f95a2bef23f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_DocumentQuarterlyReport_019c4eb7-81a7-7cc2-aac8-2f95a2bef23f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019c4eb7-81a7-7f31-87b4-d8d5e98d2cf3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_DocumentPeriodEndDate_019c4eb7-81a7-7f31-87b4-d8d5e98d2cf3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_019c4eb7-81a7-742a-8e5b-fe853e77c7c5" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_DocumentTransitionReport_019c4eb7-81a7-742a-8e5b-fe853e77c7c5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019c4eb7-81a7-7404-8642-8df7071789b3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_EntityFileNumber_019c4eb7-81a7-7404-8642-8df7071789b3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019c4eb7-81a7-74f4-9c3d-e72016d231f2" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_EntityRegistrantName_019c4eb7-81a7-74f4-9c3d-e72016d231f2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019c4eb7-81a7-71a6-a638-f0b526cb5be5" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019c4eb7-81a7-71a6-a638-f0b526cb5be5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019c4eb7-81a7-75b7-a193-592977f94984" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_EntityTaxIdentificationNumber_019c4eb7-81a7-75b7-a193-592977f94984" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019c4eb7-81a7-77c1-873b-314fea85a823" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_EntityAddressAddressLine1_019c4eb7-81a7-77c1-873b-314fea85a823" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019c4eb7-8266-747e-aaca-52495c57ec65" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_EntityAddressCityOrTown_019c4eb7-8266-747e-aaca-52495c57ec65" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019c4eb7-8266-74c1-a23d-32ba3780f218" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_EntityAddressStateOrProvince_019c4eb7-8266-74c1-a23d-32ba3780f218" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019c4eb7-8266-775d-ace8-a0cc73ea42d6" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_EntityAddressPostalZipCode_019c4eb7-8266-775d-ace8-a0cc73ea42d6" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019c4eb7-8266-7114-94c3-f9e03a3c7942" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_CityAreaCode_019c4eb7-8266-7114-94c3-f9e03a3c7942" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019c4eb7-8266-7618-82a6-490605ef2912" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_LocalPhoneNumber_019c4eb7-8266-7618-82a6-490605ef2912" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019c4eb7-8266-7e90-814e-51792800bea0" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_Security12bTitle_019c4eb7-8266-7e90-814e-51792800bea0" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019c4eb7-8266-7b54-a9c8-c4400be1b5c3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_TradingSymbol_019c4eb7-8266-7b54-a9c8-c4400be1b5c3" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019c4eb7-8266-7d7b-80fd-7c049a316525" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_SecurityExchangeName_019c4eb7-8266-7d7b-80fd-7c049a316525" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_019c4eb7-8266-700d-ae70-338dfa19ae17" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_EntityCurrentReportingStatus_019c4eb7-8266-700d-ae70-338dfa19ae17" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_019c4eb7-8266-755f-80f4-3a14320deb4f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_EntityInteractiveDataCurrent_019c4eb7-8266-755f-80f4-3a14320deb4f" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_019c4eb7-8266-778a-87f9-c1bed6a743bb" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_EntityFilerCategory_019c4eb7-8266-778a-87f9-c1bed6a743bb" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_019c4eb7-8266-76cc-9799-06f290424276" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_EntitySmallBusiness_019c4eb7-8266-76cc-9799-06f290424276" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019c4eb7-8266-7a3a-a65b-81ac3d98e69c" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_EntityEmergingGrowthCompany_019c4eb7-8266-7a3a-a65b-81ac3d98e69c" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_019c4eb7-8266-73a1-9ed2-7126d72783fd" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_EntityShellCompany_019c4eb7-8266-73a1-9ed2-7126d72783fd" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_019c4eb7-8266-7f1d-9ec4-a9c9b2484cae" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_019c4eb7-8266-7f1d-9ec4-a9c9b2484cae" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019c4eb7-8266-7788-a2d3-9423775433c9" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_AmendmentFlag_019c4eb7-8266-7788-a2d3-9423775433c9" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019c4eb7-8266-7186-bc37-e221ad2df30e" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_EntityCentralIndexKey_019c4eb7-8266-7186-bc37-e221ad2df30e" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_019c4eb7-8266-757a-8ae2-d11c660461ee" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_DocumentFiscalPeriodFocus_019c4eb7-8266-757a-8ae2-d11c660461ee" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_019c4eb7-8266-7f95-a604-8e39a372f117" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_CurrentFiscalYearEndDate_019c4eb7-8266-7f95-a604-8e39a372f117" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_019c4eb7-8266-79ee-90aa-40eed7636206" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c4eb7-81a7-7820-a11e-96a696f501d9" xlink:to="loc_dei_DocumentFiscalYearFocus_019c4eb7-8266-79ee-90aa-40eed7636206" xlink:type="arc" order="28"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="simple" xlink:href="aos-20260331.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETS"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019c4eb7-8266-77f7-b019-f6d56cb13ff4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019c4eb7-8266-779f-91c0-d140f22ced13" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019c4eb7-8266-77f7-b019-f6d56cb13ff4" xlink:to="loc_us-gaap_StatementTable_019c4eb7-8266-779f-91c0-d140f22ced13" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019c4eb7-8266-7826-89b1-d5f2cb2d7a54" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019c4eb7-8266-779f-91c0-d140f22ced13" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019c4eb7-8266-7826-89b1-d5f2cb2d7a54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-7826-89b1-d5f2cb2d7a54_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c4eb7-8266-7826-89b1-d5f2cb2d7a54" xlink:to="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-7826-89b1-d5f2cb2d7a54_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-7564-b614-c23ed4223f43" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c4eb7-8266-7826-89b1-d5f2cb2d7a54" xlink:to="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-7564-b614-c23ed4223f43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019c4eb7-8266-7008-bc87-95b02b4006b0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-7564-b614-c23ed4223f43" xlink:to="loc_us-gaap_CommonClassAMember_019c4eb7-8266-7008-bc87-95b02b4006b0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_CommonStockClassUndefinedMember_019c4eb7-8266-75f0-8498-634aa2dd2e32" xlink:href="aos-20260331.xsd#aos_CommonStockClassUndefinedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-7564-b614-c23ed4223f43" xlink:to="loc_aos_CommonStockClassUndefinedMember_019c4eb7-8266-75f0-8498-634aa2dd2e32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_019c4eb7-8266-7fb2-bf17-9ddb2496b614" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c4eb7-8266-77f7-b019-f6d56cb13ff4" xlink:to="loc_us-gaap_AssetsAbstract_019c4eb7-8266-7fb2-bf17-9ddb2496b614" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_019c4eb7-8266-7567-b4e3-6e0ef55f68d4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019c4eb7-8266-7fb2-bf17-9ddb2496b614" xlink:to="loc_us-gaap_AssetsCurrentAbstract_019c4eb7-8266-7567-b4e3-6e0ef55f68d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019c4eb7-8266-7fcd-bc9d-b0179bbcbaf4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_019c4eb7-8266-7567-b4e3-6e0ef55f68d4" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019c4eb7-8266-7fcd-bc9d-b0179bbcbaf4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesCurrent_019c4eb7-8266-7298-a27b-0c25b29d0d0f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MarketableSecuritiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_019c4eb7-8266-7567-b4e3-6e0ef55f68d4" xlink:to="loc_us-gaap_MarketableSecuritiesCurrent_019c4eb7-8266-7298-a27b-0c25b29d0d0f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivablesNetCurrent_019c4eb7-8266-760a-afa9-f6d2d0bf7320" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReceivablesNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_019c4eb7-8266-7567-b4e3-6e0ef55f68d4" xlink:to="loc_us-gaap_ReceivablesNetCurrent_019c4eb7-8266-760a-afa9-f6d2d0bf7320" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_019c4eb7-8266-7aae-87f3-836f1d4d2dd7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_019c4eb7-8266-7567-b4e3-6e0ef55f68d4" xlink:to="loc_us-gaap_InventoryNet_019c4eb7-8266-7aae-87f3-836f1d4d2dd7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsCurrent_019c4eb7-8266-77fa-831d-af00b75a8c19" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_019c4eb7-8266-7567-b4e3-6e0ef55f68d4" xlink:to="loc_us-gaap_OtherAssetsCurrent_019c4eb7-8266-77fa-831d-af00b75a8c19" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_019c4eb7-8266-7b72-876c-d9fbc3ab2b8f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_019c4eb7-8266-7567-b4e3-6e0ef55f68d4" xlink:to="loc_us-gaap_AssetsCurrent_019c4eb7-8266-7b72-876c-d9fbc3ab2b8f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_019c4eb7-8266-7cbc-beb1-bb08f06c2356" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019c4eb7-8266-7fb2-bf17-9ddb2496b614" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_019c4eb7-8266-7cbc-beb1-bb08f06c2356" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_019c4eb7-8266-73bf-940f-f89ecb6368dc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019c4eb7-8266-7fb2-bf17-9ddb2496b614" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_019c4eb7-8266-73bf-940f-f89ecb6368dc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_019c4eb7-8266-73a1-9109-deaba1337506" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019c4eb7-8266-7fb2-bf17-9ddb2496b614" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_019c4eb7-8266-73a1-9109-deaba1337506" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019c4eb7-8266-7dd8-90a6-0364d83a9f2c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019c4eb7-8266-7fb2-bf17-9ddb2496b614" xlink:to="loc_us-gaap_Goodwill_019c4eb7-8266-7dd8-90a6-0364d83a9f2c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019c4eb7-8266-7145-af95-5cca372a86a5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019c4eb7-8266-7fb2-bf17-9ddb2496b614" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019c4eb7-8266-7145-af95-5cca372a86a5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_019c4eb7-8266-7a1a-a4bb-33e10580d9b2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019c4eb7-8266-7fb2-bf17-9ddb2496b614" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_019c4eb7-8266-7a1a-a4bb-33e10580d9b2" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_019c4eb7-8266-7d2c-9a84-bac31176808d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019c4eb7-8266-7fb2-bf17-9ddb2496b614" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_019c4eb7-8266-7d2c-9a84-bac31176808d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019c4eb7-8266-7fa4-855d-c6a6e52b7f2d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019c4eb7-8266-7fb2-bf17-9ddb2496b614" xlink:to="loc_us-gaap_Assets_019c4eb7-8266-7fa4-855d-c6a6e52b7f2d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAbstract_019c4eb7-8266-72fe-a859-db6c28d8930f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c4eb7-8266-77f7-b019-f6d56cb13ff4" xlink:to="loc_us-gaap_LiabilitiesAbstract_019c4eb7-8266-72fe-a859-db6c28d8930f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_019c4eb7-8266-7e9c-baad-7396cf6214cd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019c4eb7-8266-72fe-a859-db6c28d8930f" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_019c4eb7-8266-7e9c-baad-7396cf6214cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableTradeCurrent_019c4eb7-8266-7ea7-9081-ecc3216b270d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsPayableTradeCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_019c4eb7-8266-7e9c-baad-7396cf6214cd" xlink:to="loc_us-gaap_AccountsPayableTradeCurrent_019c4eb7-8266-7ea7-9081-ecc3216b270d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_019c4eb7-8266-727c-98ff-62b9764e590d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_019c4eb7-8266-7e9c-baad-7396cf6214cd" xlink:to="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_019c4eb7-8266-727c-98ff-62b9764e590d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_019c4eb7-8266-7fb0-83ee-2101e6c5a6e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_019c4eb7-8266-7e9c-baad-7396cf6214cd" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_019c4eb7-8266-7fb0-83ee-2101e6c5a6e8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductWarrantyAccrualClassifiedCurrent_019c4eb7-8266-7071-ac1f-09394d60bafe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductWarrantyAccrualClassifiedCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_019c4eb7-8266-7e9c-baad-7396cf6214cd" xlink:to="loc_us-gaap_ProductWarrantyAccrualClassifiedCurrent_019c4eb7-8266-7071-ac1f-09394d60bafe" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_019c4eb7-8266-73e5-b821-fd8b8221bf2c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_019c4eb7-8266-7e9c-baad-7396cf6214cd" xlink:to="loc_us-gaap_LongTermDebtCurrent_019c4eb7-8266-73e5-b821-fd8b8221bf2c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_019c4eb7-8266-7647-8e95-67294ec83f6f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_019c4eb7-8266-7e9c-baad-7396cf6214cd" xlink:to="loc_us-gaap_LiabilitiesCurrent_019c4eb7-8266-7647-8e95-67294ec83f6f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_019c4eb7-8266-73af-81c5-7557d99cd8ae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019c4eb7-8266-72fe-a859-db6c28d8930f" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_019c4eb7-8266-73af-81c5-7557d99cd8ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductWarrantyAccrualNoncurrent_019c4eb7-8266-7fa2-ad49-ae32b4a3da7e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductWarrantyAccrualNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019c4eb7-8266-72fe-a859-db6c28d8930f" xlink:to="loc_us-gaap_ProductWarrantyAccrualNoncurrent_019c4eb7-8266-7fa2-ad49-ae32b4a3da7e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019c4eb7-8266-7a32-9199-2b87c7099d71" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019c4eb7-8266-72fe-a859-db6c28d8930f" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019c4eb7-8266-7a32-9199-2b87c7099d71" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_019c4eb7-8266-7c71-8a8a-502a6424817d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019c4eb7-8266-72fe-a859-db6c28d8930f" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_019c4eb7-8266-7c71-8a8a-502a6424817d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019c4eb7-8266-7d1b-8294-a1625c9e1813" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019c4eb7-8266-72fe-a859-db6c28d8930f" xlink:to="loc_us-gaap_Liabilities_019c4eb7-8266-7d1b-8294-a1625c9e1813" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityAbstract_019c4eb7-8266-7c6c-9ead-73308b55c75c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c4eb7-8266-77f7-b019-f6d56cb13ff4" xlink:to="loc_us-gaap_StockholdersEquityAbstract_019c4eb7-8266-7c6c-9ead-73308b55c75c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_019c4eb7-8266-7ef1-ab28-f8eac4af74b8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_019c4eb7-8266-7c6c-9ead-73308b55c75c" xlink:to="loc_us-gaap_CommonStockValue_019c4eb7-8266-7ef1-ab28-f8eac4af74b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_019c4eb7-8266-77fe-b37c-a7e33cfbf629" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapitalCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_019c4eb7-8266-7c6c-9ead-73308b55c75c" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_019c4eb7-8266-77fe-b37c-a7e33cfbf629" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019c4eb7-8266-79b2-81c7-cee434bda507" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_019c4eb7-8266-7c6c-9ead-73308b55c75c" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019c4eb7-8266-79b2-81c7-cee434bda507" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019c4eb7-8266-7354-9f01-29a3c6ab10b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_019c4eb7-8266-7c6c-9ead-73308b55c75c" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019c4eb7-8266-7354-9f01-29a3c6ab10b5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValue_019c4eb7-8266-70cb-87f3-dbc9e901ab9f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_019c4eb7-8266-7c6c-9ead-73308b55c75c" xlink:to="loc_us-gaap_TreasuryStockValue_019c4eb7-8266-70cb-87f3-dbc9e901ab9f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019c4eb7-8266-765d-ad52-a3008bec4fff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_019c4eb7-8266-7c6c-9ead-73308b55c75c" xlink:to="loc_us-gaap_StockholdersEquity_019c4eb7-8266-765d-ad52-a3008bec4fff" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_019c4eb7-8266-7f22-a77b-3c97c17aade7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c4eb7-8266-77f7-b019-f6d56cb13ff4" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_019c4eb7-8266-7f22-a77b-3c97c17aade7" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="simple" xlink:href="aos-20260331.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019c4eb7-8266-7f9e-9998-29ae5990d6fe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019c4eb7-8266-77cd-a17b-9c9173e2bbe6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019c4eb7-8266-7f9e-9998-29ae5990d6fe" xlink:to="loc_us-gaap_StatementTable_019c4eb7-8266-77cd-a17b-9c9173e2bbe6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019c4eb7-8266-7221-aba2-090a4fda94dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019c4eb7-8266-77cd-a17b-9c9173e2bbe6" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019c4eb7-8266-7221-aba2-090a4fda94dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-7221-aba2-090a4fda94dd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c4eb7-8266-7221-aba2-090a4fda94dd" xlink:to="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-7221-aba2-090a4fda94dd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-7bf8-8952-fc89f6b30871" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c4eb7-8266-7221-aba2-090a4fda94dd" xlink:to="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-7bf8-8952-fc89f6b30871" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019c4eb7-8266-7bd2-b6e7-02da74d3c85e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-7bf8-8952-fc89f6b30871" xlink:to="loc_us-gaap_CommonClassAMember_019c4eb7-8266-7bd2-b6e7-02da74d3c85e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_CommonStockClassUndefinedMember_019c4eb7-8266-7f94-862e-86f728bcb9d5" xlink:href="aos-20260331.xsd#aos_CommonStockClassUndefinedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-7bf8-8952-fc89f6b30871" xlink:to="loc_aos_CommonStockClassUndefinedMember_019c4eb7-8266-7f94-862e-86f728bcb9d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_019c4eb7-8266-7326-b582-7432fdcbd460" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c4eb7-8266-7f9e-9998-29ae5990d6fe" xlink:to="loc_us-gaap_CommonStockSharesIssued_019c4eb7-8266-7326-b582-7432fdcbd460" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="simple" xlink:href="aos-20260331.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019c4eb7-8266-76a3-9eec-ca35b77185c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019c4eb7-8266-7ee4-8eb6-ea919af63ebc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019c4eb7-8266-76a3-9eec-ca35b77185c8" xlink:to="loc_us-gaap_StatementTable_019c4eb7-8266-7ee4-8eb6-ea919af63ebc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019c4eb7-8266-79aa-9afb-1e77a336b3f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019c4eb7-8266-7ee4-8eb6-ea919af63ebc" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019c4eb7-8266-79aa-9afb-1e77a336b3f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c4eb7-8266-79aa-9afb-1e77a336b3f0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c4eb7-8266-79aa-9afb-1e77a336b3f0" xlink:to="loc_us-gaap_EquityComponentDomain_019c4eb7-8266-79aa-9afb-1e77a336b3f0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c4eb7-8266-74de-aa71-0937e2971c7d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c4eb7-8266-79aa-9afb-1e77a336b3f0" xlink:to="loc_us-gaap_EquityComponentDomain_019c4eb7-8266-74de-aa71-0937e2971c7d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019c4eb7-8266-75d5-823e-407347c80cad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c4eb7-8266-74de-aa71-0937e2971c7d" xlink:to="loc_us-gaap_CommonStockMember_019c4eb7-8266-75d5-823e-407347c80cad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019c4eb7-8266-7214-a15c-974ff54e9688" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c4eb7-8266-74de-aa71-0937e2971c7d" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019c4eb7-8266-7214-a15c-974ff54e9688" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019c4eb7-8266-74f8-932d-33e654f383b8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c4eb7-8266-74de-aa71-0937e2971c7d" xlink:to="loc_us-gaap_RetainedEarningsMember_019c4eb7-8266-74f8-932d-33e654f383b8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c4eb7-8266-7c79-a454-c3f15dd26033" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c4eb7-8266-74de-aa71-0937e2971c7d" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c4eb7-8266-7c79-a454-c3f15dd26033" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_019c4eb7-8266-7ab1-a231-98461d2dc809" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c4eb7-8266-74de-aa71-0937e2971c7d" xlink:to="loc_us-gaap_TreasuryStockCommonMember_019c4eb7-8266-7ab1-a231-98461d2dc809" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019c4eb7-8266-739a-87bc-f572f063c997" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019c4eb7-8266-7ee4-8eb6-ea919af63ebc" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019c4eb7-8266-739a-87bc-f572f063c997" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-739a-87bc-f572f063c997_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c4eb7-8266-739a-87bc-f572f063c997" xlink:to="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-739a-87bc-f572f063c997_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-7a3d-a915-ef4ddf983f89" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c4eb7-8266-739a-87bc-f572f063c997" xlink:to="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-7a3d-a915-ef4ddf983f89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019c4eb7-8266-7c77-bcfe-7ed4307dcf4b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-7a3d-a915-ef4ddf983f89" xlink:to="loc_us-gaap_CommonClassAMember_019c4eb7-8266-7c77-bcfe-7ed4307dcf4b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_CommonStockClassUndefinedMember_019c4eb7-8266-79b8-98fc-9baa2cd7121e" xlink:href="aos-20260331.xsd#aos_CommonStockClassUndefinedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c4eb7-8266-7a3d-a915-ef4ddf983f89" xlink:to="loc_aos_CommonStockClassUndefinedMember_019c4eb7-8266-79b8-98fc-9baa2cd7121e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c4eb7-8266-71fe-8578-1d30c7d7b40f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c4eb7-8266-76a3-9eec-ca35b77185c8" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c4eb7-8266-71fe-8578-1d30c7d7b40f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019c4eb7-8266-789c-a2e1-667b681bf023" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c4eb7-8266-71fe-8578-1d30c7d7b40f" xlink:to="loc_us-gaap_StockholdersEquity_019c4eb7-8266-789c-a2e1-667b681bf023" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_019c4eb7-8266-7552-80a0-9d8799eaeed3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c4eb7-8266-71fe-8578-1d30c7d7b40f" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_019c4eb7-8266-7552-80a0-9d8799eaeed3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_AdjustmentsToAdditionalPaidInCapitalShareUnitsIssued_019c4eb7-8266-7b9c-a205-7c7edb5655c5" xlink:href="aos-20260331.xsd#aos_AdjustmentsToAdditionalPaidInCapitalShareUnitsIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c4eb7-8266-71fe-8578-1d30c7d7b40f" xlink:to="loc_aos_AdjustmentsToAdditionalPaidInCapitalShareUnitsIssued_019c4eb7-8266-7b9c-a205-7c7edb5655c5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_VestingOfShareUnits_019c4eb7-8266-78bb-86a8-58353a5c8861" xlink:href="aos-20260331.xsd#aos_VestingOfShareUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c4eb7-8266-71fe-8578-1d30c7d7b40f" xlink:to="loc_aos_VestingOfShareUnits_019c4eb7-8266-78bb-86a8-58353a5c8861" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019c4eb7-8266-75b3-a62b-252bee194745" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c4eb7-8266-71fe-8578-1d30c7d7b40f" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019c4eb7-8266-75b3-a62b-252bee194745" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_019c4eb7-8266-737c-ac11-ce2fd18966be" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c4eb7-8266-71fe-8578-1d30c7d7b40f" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_019c4eb7-8266-737c-ac11-ce2fd18966be" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_019c4eb7-8266-726b-bbd3-b411ad3946b2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c4eb7-8266-71fe-8578-1d30c7d7b40f" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_019c4eb7-8266-726b-bbd3-b411ad3946b2" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019c4eb7-8266-7720-86c0-46fbfbad5471" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c4eb7-8266-71fe-8578-1d30c7d7b40f" xlink:to="loc_us-gaap_NetIncomeLoss_019c4eb7-8266-7720-86c0-46fbfbad5471" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_019c4eb7-8266-7594-8831-8a6fcfaba280" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendsCommonStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c4eb7-8266-71fe-8578-1d30c7d7b40f" xlink:to="loc_us-gaap_DividendsCommonStockCash_019c4eb7-8266-7594-8831-8a6fcfaba280" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019c4eb7-8266-72b8-8402-73518ec899d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c4eb7-8266-71fe-8578-1d30c7d7b40f" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019c4eb7-8266-72b8-8402-73518ec899d9" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_ExciseTaxOnRepurchasesOfCommonStock_019c4eb7-8266-7cbe-b4d8-b9de971bda30" xlink:href="aos-20260331.xsd#aos_ExciseTaxOnRepurchasesOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c4eb7-8266-71fe-8578-1d30c7d7b40f" xlink:to="loc_aos_ExciseTaxOnRepurchasesOfCommonStock_019c4eb7-8266-7cbe-b4d8-b9de971bda30" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019c4eb7-8266-7059-b9fd-ac58660f58b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/RevenueRecognitionNarrativeDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#RevenueRecognitionNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/RevenueRecognitionNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019c4eb7-8266-7de2-92f1-37e316e66161" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019c4eb7-8266-7ad6-ab1a-99ff1075ae75" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c4eb7-8266-7de2-92f1-37e316e66161" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019c4eb7-8266-7ad6-ab1a-99ff1075ae75" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019c4eb7-8266-736a-b253-1e13882e53d3" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c4eb7-8266-7ad6-ab1a-99ff1075ae75" xlink:to="loc_srt_RangeAxis_019c4eb7-8266-736a-b253-1e13882e53d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019c4eb7-8266-736a-b253-1e13882e53d3_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019c4eb7-8266-736a-b253-1e13882e53d3" xlink:to="loc_srt_RangeMember_019c4eb7-8266-736a-b253-1e13882e53d3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019c4eb7-8266-78ed-88d9-c2145272b6d2" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019c4eb7-8266-736a-b253-1e13882e53d3" xlink:to="loc_srt_RangeMember_019c4eb7-8266-78ed-88d9-c2145272b6d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019c4eb7-8266-7f94-a499-ad2f48973c47" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019c4eb7-8266-78ed-88d9-c2145272b6d2" xlink:to="loc_srt_MinimumMember_019c4eb7-8266-7f94-a499-ad2f48973c47" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019c4eb7-8266-7829-a82c-1e3b5dff508e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019c4eb7-8266-78ed-88d9-c2145272b6d2" xlink:to="loc_srt_MaximumMember_019c4eb7-8266-7829-a82c-1e3b5dff508e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019c4eb7-8266-7d68-bd6d-6306325f6dc9" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c4eb7-8266-7ad6-ab1a-99ff1075ae75" xlink:to="loc_srt_ProductOrServiceAxis_019c4eb7-8266-7d68-bd6d-6306325f6dc9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c4eb7-8266-7d68-bd6d-6306325f6dc9_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019c4eb7-8266-7d68-bd6d-6306325f6dc9" xlink:to="loc_srt_ProductsAndServicesDomain_019c4eb7-8266-7d68-bd6d-6306325f6dc9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c4eb7-8266-7dec-9bfb-0f36fff1d401" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019c4eb7-8266-7d68-bd6d-6306325f6dc9" xlink:to="loc_srt_ProductsAndServicesDomain_019c4eb7-8266-7dec-9bfb-0f36fff1d401" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_WaterHeatersMember_019c4eb7-8266-7293-ae07-77828dc9f517" xlink:href="aos-20260331.xsd#aos_WaterHeatersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c4eb7-8266-7dec-9bfb-0f36fff1d401" xlink:to="loc_aos_WaterHeatersMember_019c4eb7-8266-7293-ae07-77828dc9f517" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019c4eb7-8266-79be-80ab-8d5565d6e3c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c4eb7-8266-7ad6-ab1a-99ff1075ae75" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019c4eb7-8266-79be-80ab-8d5565d6e3c5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c4eb7-8266-79be-80ab-8d5565d6e3c5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c4eb7-8266-79be-80ab-8d5565d6e3c5" xlink:to="loc_us-gaap_SegmentDomain_019c4eb7-8266-79be-80ab-8d5565d6e3c5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c4eb7-8266-7bb1-b1f4-a19ce42a10ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c4eb7-8266-79be-80ab-8d5565d6e3c5" xlink:to="loc_us-gaap_SegmentDomain_019c4eb7-8266-7bb1-b1f4-a19ce42a10ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_NorthAmericaSegmentMember_019c4eb7-8266-7bde-9adb-71171040592e" xlink:href="aos-20260331.xsd#aos_NorthAmericaSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019c4eb7-8266-7bb1-b1f4-a19ce42a10ff" xlink:to="loc_aos_NorthAmericaSegmentMember_019c4eb7-8266-7bde-9adb-71171040592e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_RevenueFromContractWithCustomerPaymentTerms_019c4eb7-8266-7be8-8b44-a376b90ca38d" xlink:href="aos-20260331.xsd#aos_RevenueFromContractWithCustomerPaymentTerms"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c4eb7-8266-7de2-92f1-37e316e66161" xlink:to="loc_aos_RevenueFromContractWithCustomerPaymentTerms_019c4eb7-8266-7be8-8b44-a376b90ca38d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_019c4eb7-8266-7afd-afcd-7a1619434c3b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c4eb7-8266-7de2-92f1-37e316e66161" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_019c4eb7-8266-7afd-afcd-7a1619434c3b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_019c4eb7-8266-73a3-941f-21227cc45631" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c4eb7-8266-7de2-92f1-37e316e66161" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_019c4eb7-8266-73a3-941f-21227cc45631" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportableSegments_019c4eb7-8266-7f7e-9c07-8145bcf18ad5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NumberOfReportableSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c4eb7-8266-7de2-92f1-37e316e66161" xlink:to="loc_us-gaap_NumberOfReportableSegments_019c4eb7-8266-7f7e-9c07-8145bcf18ad5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_NumberOfWholesaleDistributors_019c4eb7-8266-7a2e-80e2-b30b25da49f6" xlink:href="aos-20260331.xsd#aos_NumberOfWholesaleDistributors"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c4eb7-8266-7de2-92f1-37e316e66161" xlink:to="loc_aos_NumberOfWholesaleDistributors_019c4eb7-8266-7a2e-80e2-b30b25da49f6" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/RevenueRecognitionScheduleofSegmentSalesDisaggregatedbyMajorProductLineDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#RevenueRecognitionScheduleofSegmentSalesDisaggregatedbyMajorProductLineDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/RevenueRecognitionScheduleofSegmentSalesDisaggregatedbyMajorProductLineDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019c4eb7-8266-74c7-a564-9a01fd674700" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019c4eb7-8266-75d1-ba48-09718cb3af8a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c4eb7-8266-74c7-a564-9a01fd674700" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019c4eb7-8266-75d1-ba48-09718cb3af8a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019c4eb7-8266-70c0-836a-6a5118835fbf" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c4eb7-8266-75d1-ba48-09718cb3af8a" xlink:to="loc_srt_ConsolidationItemsAxis_019c4eb7-8266-70c0-836a-6a5118835fbf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-70c0-836a-6a5118835fbf_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019c4eb7-8266-70c0-836a-6a5118835fbf" xlink:to="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-70c0-836a-6a5118835fbf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7bb8-ad1d-8718c94f9b1b" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019c4eb7-8266-70c0-836a-6a5118835fbf" xlink:to="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7bb8-ad1d-8718c94f9b1b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019c4eb7-8266-795e-9062-d9dcdf1733c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7bb8-ad1d-8718c94f9b1b" xlink:to="loc_us-gaap_OperatingSegmentsMember_019c4eb7-8266-795e-9062-d9dcdf1733c5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntersegmentEliminationMember_019c4eb7-8266-73c6-b95f-726ac433d11e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IntersegmentEliminationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7bb8-ad1d-8718c94f9b1b" xlink:to="loc_us-gaap_IntersegmentEliminationMember_019c4eb7-8266-73c6-b95f-726ac433d11e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019c4eb7-8266-7bc2-9693-3906839790cf" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c4eb7-8266-75d1-ba48-09718cb3af8a" xlink:to="loc_srt_ProductOrServiceAxis_019c4eb7-8266-7bc2-9693-3906839790cf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c4eb7-8266-7bc2-9693-3906839790cf_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019c4eb7-8266-7bc2-9693-3906839790cf" xlink:to="loc_srt_ProductsAndServicesDomain_019c4eb7-8266-7bc2-9693-3906839790cf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c4eb7-8266-7f92-bc2e-7c69a8c3d58d" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019c4eb7-8266-7bc2-9693-3906839790cf" xlink:to="loc_srt_ProductsAndServicesDomain_019c4eb7-8266-7f92-bc2e-7c69a8c3d58d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_WaterHeatersAndRelatedPartsMember_019c4eb7-8266-7f32-a8b8-ec533a2ff43a" xlink:href="aos-20260331.xsd#aos_WaterHeatersAndRelatedPartsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c4eb7-8266-7f92-bc2e-7c69a8c3d58d" xlink:to="loc_aos_WaterHeatersAndRelatedPartsMember_019c4eb7-8266-7f32-a8b8-ec533a2ff43a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_BoilersRelatedPartsAndComponentsMember_019c4eb7-8266-714d-b7cb-fc812db203bc" xlink:href="aos-20260331.xsd#aos_BoilersRelatedPartsAndComponentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c4eb7-8266-7f92-bc2e-7c69a8c3d58d" xlink:to="loc_aos_BoilersRelatedPartsAndComponentsMember_019c4eb7-8266-714d-b7cb-fc812db203bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_WaterTreatmentProductsAndRelatedPartsMember_019c4eb7-8266-7038-a1f8-6b1ca4506e5c" xlink:href="aos-20260331.xsd#aos_WaterTreatmentProductsAndRelatedPartsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c4eb7-8266-7f92-bc2e-7c69a8c3d58d" xlink:to="loc_aos_WaterTreatmentProductsAndRelatedPartsMember_019c4eb7-8266-7038-a1f8-6b1ca4506e5c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019c4eb7-8266-7379-87df-0ad23f333785" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c4eb7-8266-75d1-ba48-09718cb3af8a" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019c4eb7-8266-7379-87df-0ad23f333785" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c4eb7-8266-7379-87df-0ad23f333785_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c4eb7-8266-7379-87df-0ad23f333785" xlink:to="loc_us-gaap_SegmentDomain_019c4eb7-8266-7379-87df-0ad23f333785_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c4eb7-8266-75bf-948c-7c8c5273d941" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c4eb7-8266-7379-87df-0ad23f333785" xlink:to="loc_us-gaap_SegmentDomain_019c4eb7-8266-75bf-948c-7c8c5273d941" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_NorthAmericaSegmentMember_019c4eb7-8266-7d5c-add0-8b2efa4bfa8c" xlink:href="aos-20260331.xsd#aos_NorthAmericaSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019c4eb7-8266-75bf-948c-7c8c5273d941" xlink:to="loc_aos_NorthAmericaSegmentMember_019c4eb7-8266-7d5c-add0-8b2efa4bfa8c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_RestOfWorldMember_019c4eb7-8266-7882-810f-1071a85878d2" xlink:href="aos-20260331.xsd#aos_RestOfWorldMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019c4eb7-8266-75bf-948c-7c8c5273d941" xlink:to="loc_aos_RestOfWorldMember_019c4eb7-8266-7882-810f-1071a85878d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019c4eb7-8266-7e74-a7ee-7deefc071687" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c4eb7-8266-75d1-ba48-09718cb3af8a" xlink:to="loc_srt_StatementGeographicalAxis_019c4eb7-8266-7e74-a7ee-7deefc071687" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019c4eb7-8266-7e74-a7ee-7deefc071687_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019c4eb7-8266-7e74-a7ee-7deefc071687" xlink:to="loc_srt_SegmentGeographicalDomain_019c4eb7-8266-7e74-a7ee-7deefc071687_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019c4eb7-8266-7c4a-88e3-55a7b480ea2e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019c4eb7-8266-7e74-a7ee-7deefc071687" xlink:to="loc_srt_SegmentGeographicalDomain_019c4eb7-8266-7c4a-88e3-55a7b480ea2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CN_019c4eb7-8266-7634-931e-248569cd3383" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_CN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019c4eb7-8266-7c4a-88e3-55a7b480ea2e" xlink:to="loc_country_CN_019c4eb7-8266-7634-931e-248569cd3383" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_AllOtherRestOfWorldMember_019c4eb7-8266-7c17-bd6f-b9f29d14675b" xlink:href="aos-20260331.xsd#aos_AllOtherRestOfWorldMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019c4eb7-8266-7c4a-88e3-55a7b480ea2e" xlink:to="loc_aos_AllOtherRestOfWorldMember_019c4eb7-8266-7c17-bd6f-b9f29d14675b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019dbee8-22fe-7fba-bf1b-fb5eabd6adf9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c4eb7-8266-75d1-ba48-09718cb3af8a" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019dbee8-22fe-7fba-bf1b-fb5eabd6adf9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019dbee8-22fe-7fba-bf1b-fb5eabd6adf9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019dbee8-22fe-7fba-bf1b-fb5eabd6adf9" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019dbee8-22fe-7fba-bf1b-fb5eabd6adf9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019dbee8-22fe-7b5c-8f28-f30c5de47c81" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019dbee8-22fe-7fba-bf1b-fb5eabd6adf9" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019dbee8-22fe-7b5c-8f28-f30c5de47c81" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_LeonardValueMember_019dbee8-5788-74fa-b96e-78e264f73a47" xlink:href="aos-20260331.xsd#aos_LeonardValueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019dbee8-22fe-7b5c-8f28-f30c5de47c81" xlink:to="loc_aos_LeonardValueMember_019dbee8-5788-74fa-b96e-78e264f73a47" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c4eb7-8266-7918-a031-69ad97ea11c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c4eb7-8266-74c7-a564-9a01fd674700" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c4eb7-8266-7918-a031-69ad97ea11c9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_019dda27-781a-7cef-9b33-ddd892033265" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c4eb7-8266-74c7-a564-9a01fd674700" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_019dda27-781a-7cef-9b33-ddd892033265" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/AcquisitionsNarrativeDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#AcquisitionsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/AcquisitionsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_019d91ac-d964-751f-ba14-ff36c08816f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfImpairedLongLivedAssetsHeldAndUsedTable_019c4eb7-8266-7cee-b7d2-ef1dd51c7fe4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfImpairedLongLivedAssetsHeldAndUsedTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_019d91ac-d964-751f-ba14-ff36c08816f7" xlink:to="loc_us-gaap_ScheduleOfImpairedLongLivedAssetsHeldAndUsedTable_019c4eb7-8266-7cee-b7d2-ef1dd51c7fe4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019d91ac-d964-739e-8196-d2b4abd02e69" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfImpairedLongLivedAssetsHeldAndUsedTable_019c4eb7-8266-7cee-b7d2-ef1dd51c7fe4" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019d91ac-d964-739e-8196-d2b4abd02e69" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019d91ac-d964-739e-8196-d2b4abd02e69_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019d91ac-d964-739e-8196-d2b4abd02e69" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019d91ac-d964-739e-8196-d2b4abd02e69_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019d91ac-d964-7d3e-8270-38fa37b07262" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019d91ac-d964-739e-8196-d2b4abd02e69" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019d91ac-d964-7d3e-8270-38fa37b07262" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_LeonardValueMember_019d91ac-d964-7afb-8b42-f785d466894d" xlink:href="aos-20260331.xsd#aos_LeonardValueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019d91ac-d964-7d3e-8270-38fa37b07262" xlink:to="loc_aos_LeonardValueMember_019d91ac-d964-7afb-8b42-f785d466894d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_019d91ac-d964-7525-88ba-3eb83dc3d0af" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfImpairedLongLivedAssetsHeldAndUsedTable_019c4eb7-8266-7cee-b7d2-ef1dd51c7fe4" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_019d91ac-d964-7525-88ba-3eb83dc3d0af" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019d91ac-d964-7525-88ba-3eb83dc3d0af_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_019d91ac-d964-7525-88ba-3eb83dc3d0af" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019d91ac-d964-7525-88ba-3eb83dc3d0af_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019d91ac-d964-79d6-af30-1786f9faead5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_019d91ac-d964-7525-88ba-3eb83dc3d0af" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019d91ac-d964-79d6-af30-1786f9faead5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksMember_019d91ac-d964-789c-907e-1ee8dc078367" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TrademarksMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019d91ac-d964-79d6-af30-1786f9faead5" xlink:to="loc_us-gaap_TrademarksMember_019d91ac-d964-789c-907e-1ee8dc078367" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019d91ac-d964-7029-858f-4b190fd07033" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfImpairedLongLivedAssetsHeldAndUsedTable_019c4eb7-8266-7cee-b7d2-ef1dd51c7fe4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019d91ac-d964-7029-858f-4b190fd07033" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019d91ac-d964-7029-858f-4b190fd07033_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019d91ac-d964-7029-858f-4b190fd07033" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019d91ac-d964-7029-858f-4b190fd07033_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019d91ac-d964-78b0-95c7-0bd017cf61fd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019d91ac-d964-7029-858f-4b190fd07033" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019d91ac-d964-78b0-95c7-0bd017cf61fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PatentsMember_019d91ac-d964-7303-a6b7-0506974c982c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PatentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019d91ac-d964-78b0-95c7-0bd017cf61fd" xlink:to="loc_us-gaap_PatentsMember_019d91ac-d964-7303-a6b7-0506974c982c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_019d91ac-d964-73a0-9424-3acb991d7d64" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019d91ac-d964-78b0-95c7-0bd017cf61fd" xlink:to="loc_us-gaap_CustomerRelationshipsMember_019d91ac-d964-73a0-9424-3acb991d7d64" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019dbabd-19f5-7951-8625-e33fd3e1a4bc" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfImpairedLongLivedAssetsHeldAndUsedTable_019c4eb7-8266-7cee-b7d2-ef1dd51c7fe4" xlink:to="loc_srt_RangeAxis_019dbabd-19f5-7951-8625-e33fd3e1a4bc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019dbabd-19f5-7951-8625-e33fd3e1a4bc_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019dbabd-19f5-7951-8625-e33fd3e1a4bc" xlink:to="loc_srt_RangeMember_019dbabd-19f5-7951-8625-e33fd3e1a4bc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019dbabd-19f5-712d-b9dc-f69604c2e59e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019dbabd-19f5-7951-8625-e33fd3e1a4bc" xlink:to="loc_srt_RangeMember_019dbabd-19f5-712d-b9dc-f69604c2e59e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019dbabd-7988-789d-8b30-78cbf61052d2" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019dbabd-19f5-712d-b9dc-f69604c2e59e" xlink:to="loc_srt_MinimumMember_019dbabd-7988-789d-8b30-78cbf61052d2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019dbabd-3a02-78d4-af91-cd2491ff08f2" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019dbabd-19f5-712d-b9dc-f69604c2e59e" xlink:to="loc_srt_MaximumMember_019dbabd-3a02-78d4-af91-cd2491ff08f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_019d94c1-d5ae-7fa7-a0d0-3f26f336d6c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_019d91ac-d964-751f-ba14-ff36c08816f7" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_019d94c1-d5ae-7fa7-a0d0-3f26f336d6c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019dbef7-311e-779e-8e9d-b047ca7bd389" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_019d91ac-d964-751f-ba14-ff36c08816f7" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019dbef7-311e-779e-8e9d-b047ca7bd389" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EscrowDeposit_019d91ac-d964-728e-b57e-ad0465057f8c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EscrowDeposit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_019d91ac-d964-751f-ba14-ff36c08816f7" xlink:to="loc_us-gaap_EscrowDeposit_019d91ac-d964-728e-b57e-ad0465057f8c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_019d91ac-d964-7af7-90ef-4771d45035a3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_019d91ac-d964-751f-ba14-ff36c08816f7" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_019d91ac-d964-7af7-90ef-4771d45035a3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_019d91ac-d964-71a6-a09a-517fc29d1489" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_019d91ac-d964-751f-ba14-ff36c08816f7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_019d91ac-d964-71a6-a09a-517fc29d1489" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIndefiniteLivedIntangibleAssets_019d91ac-d964-72e8-b43c-b78e9bbcae31" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIndefiniteLivedIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_019d91ac-d964-751f-ba14-ff36c08816f7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIndefiniteLivedIntangibleAssets_019d91ac-d964-72e8-b43c-b78e9bbcae31" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_019d91ac-d964-744b-90f4-e70a0cb4cbff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_019d91ac-d964-751f-ba14-ff36c08816f7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_019d91ac-d964-744b-90f4-e70a0cb4cbff" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_019d91ac-d964-7513-9a7f-0166c5a52bb8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_019d91ac-d964-751f-ba14-ff36c08816f7" xlink:to="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_019d91ac-d964-7513-9a7f-0166c5a52bb8" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_019d91ac-eeb5-7fc2-b329-cddcfecd1313" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_019d91ac-d964-751f-ba14-ff36c08816f7" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_019d91ac-eeb5-7fc2-b329-cddcfecd1313" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual_019d91ac-eeb5-76ae-9ce1-ff919892e0e4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems_019d91ac-d964-751f-ba14-ff36c08816f7" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual_019d91ac-eeb5-76ae-9ce1-ff919892e0e4" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/AcquisitionsScheduleoftheAllocationoftheFairValueoftheAssetsAcquiredandLiabilitiesAssumedattheDateofAcquisitionDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#AcquisitionsScheduleoftheAllocationoftheFairValueoftheAssetsAcquiredandLiabilitiesAssumedattheDateofAcquisitionDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/AcquisitionsScheduleoftheAllocationoftheFairValueoftheAssetsAcquiredandLiabilitiesAssumedattheDateofAcquisitionDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_019c4eb7-8266-7fed-bb48-b0233399330a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019c4eb7-8266-7298-a2ff-310709fe184d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019c4eb7-8266-7fed-bb48-b0233399330a" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019c4eb7-8266-7298-a2ff-310709fe184d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019c4eb7-8266-7c0f-8264-5aeef7a3acb9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019c4eb7-8266-7298-a2ff-310709fe184d" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019c4eb7-8266-7c0f-8264-5aeef7a3acb9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019c4eb7-8266-7c0f-8264-5aeef7a3acb9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019c4eb7-8266-7c0f-8264-5aeef7a3acb9" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019c4eb7-8266-7c0f-8264-5aeef7a3acb9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019c4eb7-8266-7408-a5d8-1713bb4dc132" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019c4eb7-8266-7c0f-8264-5aeef7a3acb9" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019c4eb7-8266-7408-a5d8-1713bb4dc132" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_LeonardValueMember_019d4901-dd06-79f3-8d99-789c154ac0d1" xlink:href="aos-20260331.xsd#aos_LeonardValueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019c4eb7-8266-7408-a5d8-1713bb4dc132" xlink:to="loc_aos_LeonardValueMember_019d4901-dd06-79f3-8d99-789c154ac0d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_019c4eb7-8266-7949-b423-d395f2419a7c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019c4eb7-8266-7fed-bb48-b0233399330a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_019c4eb7-8266-7949-b423-d395f2419a7c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_019c4eb7-8266-77ce-84a2-6fbfe6138fbf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019c4eb7-8266-7fed-bb48-b0233399330a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_019c4eb7-8266-77ce-84a2-6fbfe6138fbf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_019c4eb7-8266-73fe-bba0-49441cf815d5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019c4eb7-8266-7fed-bb48-b0233399330a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_019c4eb7-8266-73fe-bba0-49441cf815d5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019c4eb7-8266-7f63-bf4b-5c4274e0dc50" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019c4eb7-8266-7fed-bb48-b0233399330a" xlink:to="loc_us-gaap_Goodwill_019c4eb7-8266-7f63-bf4b-5c4274e0dc50" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_019d9199-d6cf-7df8-b87d-fa6caea7ce64" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019c4eb7-8266-7fed-bb48-b0233399330a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_019d9199-d6cf-7df8-b87d-fa6caea7ce64" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsIncludingGoodwill_019c4eb7-8266-7fd5-a46b-d240752a7994" xlink:href="aos-20260331.xsd#aos_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsIncludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019c4eb7-8266-7fed-bb48-b0233399330a" xlink:to="loc_aos_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsIncludingGoodwill_019c4eb7-8266-7fd5-a46b-d240752a7994" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_019c4eb7-8266-7db9-8cf9-b3d52f8a25ab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019c4eb7-8266-7fed-bb48-b0233399330a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_019c4eb7-8266-7db9-8cf9-b3d52f8a25ab" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_019d919a-b468-746b-8c9a-2ba9e2368a9c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019c4eb7-8266-7fed-bb48-b0233399330a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_019d919a-b468-746b-8c9a-2ba9e2368a9c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_019c4eb7-8266-7a16-9791-920d1d131a35" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019c4eb7-8266-7fed-bb48-b0233399330a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_019c4eb7-8266-7a16-9791-920d1d131a35" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/DebtDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#DebtDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/DebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_019dbef3-c73c-7db2-a509-8bed7256d5c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_019cd20e-852f-78c8-bad9-e11be2f999bd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019dbef3-c73c-7db2-a509-8bed7256d5c8" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_019cd20e-852f-78c8-bad9-e11be2f999bd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019dbef3-c73c-7996-8b23-338cfde56967" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_019cd20e-852f-78c8-bad9-e11be2f999bd" xlink:to="loc_us-gaap_CreditFacilityAxis_019dbef3-c73c-7996-8b23-338cfde56967" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019dbef3-c73c-7996-8b23-338cfde56967_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019dbef3-c73c-7996-8b23-338cfde56967" xlink:to="loc_us-gaap_CreditFacilityDomain_019dbef3-c73c-7996-8b23-338cfde56967_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019dbef3-c73c-7863-8da3-339bdfac653c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019dbef3-c73c-7996-8b23-338cfde56967" xlink:to="loc_us-gaap_CreditFacilityDomain_019dbef3-c73c-7863-8da3-339bdfac653c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019dbef3-c73c-7029-babc-8db7e3faa141" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019dbef3-c73c-7863-8da3-339bdfac653c" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019dbef3-c73c-7029-babc-8db7e3faa141" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_019dbef3-c73c-758a-8439-9dadd779b5c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019dbef3-c73c-7863-8da3-339bdfac653c" xlink:to="loc_us-gaap_SecuredDebtMember_019dbef3-c73c-758a-8439-9dadd779b5c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019dbef3-c73c-7c20-af25-e90404704e8a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_019cd20e-852f-78c8-bad9-e11be2f999bd" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019dbef3-c73c-7c20-af25-e90404704e8a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019dbef3-c73c-7c20-af25-e90404704e8a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019dbef3-c73c-7c20-af25-e90404704e8a" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019dbef3-c73c-7c20-af25-e90404704e8a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019dbef3-c73c-73e1-a278-1914592b4820" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019dbef3-c73c-7c20-af25-e90404704e8a" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019dbef3-c73c-73e1-a278-1914592b4820" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019dbef3-c73c-7ce7-ab6a-95b5179176f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019dbef3-c73c-73e1-a278-1914592b4820" xlink:to="loc_us-gaap_LineOfCreditMember_019dbef3-c73c-7ce7-ab6a-95b5179176f7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019dbef3-c73c-7bf0-b498-8bea6a11abd6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019dbef3-c73c-7db2-a509-8bed7256d5c8" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019dbef3-c73c-7bf0-b498-8bea6a11abd6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_LineOfCreditFacilityAccordionFeatureHigherBorrowingCapacityOption_019dbef3-c73c-7f9b-a017-378eed03d639" xlink:href="aos-20260331.xsd#aos_LineOfCreditFacilityAccordionFeatureHigherBorrowingCapacityOption"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019dbef3-c73c-7db2-a509-8bed7256d5c8" xlink:to="loc_aos_LineOfCreditFacilityAccordionFeatureHigherBorrowingCapacityOption_019dbef3-c73c-7f9b-a017-378eed03d639" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_LineOfCreditFacilityFinancialCovenantRequiredNumber_019dbef3-c73c-785f-9bdf-882445324a9e" xlink:href="aos-20260331.xsd#aos_LineOfCreditFacilityFinancialCovenantRequiredNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019dbef3-c73c-7db2-a509-8bed7256d5c8" xlink:to="loc_aos_LineOfCreditFacilityFinancialCovenantRequiredNumber_019dbef3-c73c-785f-9bdf-882445324a9e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_019dbef3-c73c-744c-bd01-ddcf7c24a028" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019dbef3-c73c-7db2-a509-8bed7256d5c8" xlink:to="loc_us-gaap_DebtInstrumentTerm_019dbef3-c73c-744c-bd01-ddcf7c24a028" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019dbef3-c73c-7753-8e52-410c91773d91" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019dbef3-c73c-7db2-a509-8bed7256d5c8" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019dbef3-c73c-7753-8e52-410c91773d91" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_NumberOfBanks_019dbef3-c73c-797f-ae0b-5593bd046c85" xlink:href="aos-20260331.xsd#aos_NumberOfBanks"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019dbef3-c73c-7db2-a509-8bed7256d5c8" xlink:to="loc_aos_NumberOfBanks_019dbef3-c73c-797f-ae0b-5593bd046c85" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019dbef3-c73c-7f9d-93e9-170ea549bd87" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019dbef3-c73c-7db2-a509-8bed7256d5c8" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019dbef3-c73c-7f9d-93e9-170ea549bd87" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateDuringPeriod_019dbef3-c73c-7b52-a3c3-401b5505c877" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentInterestRateDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019dbef3-c73c-7db2-a509-8bed7256d5c8" xlink:to="loc_us-gaap_DebtInstrumentInterestRateDuringPeriod_019dbef3-c73c-7b52-a3c3-401b5505c877" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/ShareBasedCompensationNarrativeDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#ShareBasedCompensationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/ShareBasedCompensationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c4eb7-8266-71ec-8528-a908cead5892" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019c4eb7-8266-7ff5-bae6-485957d17564" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c4eb7-8266-71ec-8528-a908cead5892" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019c4eb7-8266-7ff5-bae6-485957d17564" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_019c4eb7-8266-713f-9e67-0d200865615a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019c4eb7-8266-7ff5-bae6-485957d17564" xlink:to="loc_us-gaap_PlanNameAxis_019c4eb7-8266-713f-9e67-0d200865615a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_019c4eb7-8266-713f-9e67-0d200865615a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_019c4eb7-8266-713f-9e67-0d200865615a" xlink:to="loc_us-gaap_PlanNameDomain_019c4eb7-8266-713f-9e67-0d200865615a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_019c4eb7-8266-7a65-a413-60ed6c923450" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_019c4eb7-8266-713f-9e67-0d200865615a" xlink:to="loc_us-gaap_PlanNameDomain_019c4eb7-8266-7a65-a413-60ed6c923450" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_AOSmithCombinedCompensationPlanMember_019c4eb7-8266-7916-b674-212accdfd8a8" xlink:href="aos-20260331.xsd#aos_AOSmithCombinedCompensationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_019c4eb7-8266-7a65-a413-60ed6c923450" xlink:to="loc_aos_AOSmithCombinedCompensationPlanMember_019c4eb7-8266-7916-b674-212accdfd8a8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019c4eb7-8266-7acb-b72b-a33849000368" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019c4eb7-8266-7ff5-bae6-485957d17564" xlink:to="loc_us-gaap_AwardTypeAxis_019c4eb7-8266-7acb-b72b-a33849000368" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c4eb7-8266-7acb-b72b-a33849000368_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019c4eb7-8266-7acb-b72b-a33849000368" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c4eb7-8266-7acb-b72b-a33849000368_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c4eb7-8266-7ae4-881c-50fa4c1b67b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019c4eb7-8266-7acb-b72b-a33849000368" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c4eb7-8266-7ae4-881c-50fa4c1b67b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019c4eb7-8266-7f0f-bc07-610b9c87872a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c4eb7-8266-7ae4-881c-50fa4c1b67b6" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019c4eb7-8266-7f0f-bc07-610b9c87872a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_019c4eb7-8266-73ec-87ac-9608bf6b1b26" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c4eb7-8266-7ae4-881c-50fa4c1b67b6" xlink:to="loc_us-gaap_PerformanceSharesMember_019c4eb7-8266-73ec-87ac-9608bf6b1b26" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019c4eb7-8266-7744-8d93-b88cba0805cc" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019c4eb7-8266-7ff5-bae6-485957d17564" xlink:to="loc_srt_RangeAxis_019c4eb7-8266-7744-8d93-b88cba0805cc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019c4eb7-8266-7744-8d93-b88cba0805cc_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019c4eb7-8266-7744-8d93-b88cba0805cc" xlink:to="loc_srt_RangeMember_019c4eb7-8266-7744-8d93-b88cba0805cc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019c4eb7-8266-7e58-9daa-beee19bef34f" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019c4eb7-8266-7744-8d93-b88cba0805cc" xlink:to="loc_srt_RangeMember_019c4eb7-8266-7e58-9daa-beee19bef34f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019c4eb7-8266-7fef-aee3-0aaea5bd3902" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019c4eb7-8266-7e58-9daa-beee19bef34f" xlink:to="loc_srt_MinimumMember_019c4eb7-8266-7fef-aee3-0aaea5bd3902" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019c4eb7-8266-72aa-8a4a-74d71486e6c4" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019c4eb7-8266-7e58-9daa-beee19bef34f" xlink:to="loc_srt_MaximumMember_019c4eb7-8266-72aa-8a4a-74d71486e6c4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_019c4eb7-8266-7e4a-949d-605e6a1e895f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c4eb7-8266-71ec-8528-a908cead5892" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_019c4eb7-8266-7e4a-949d-605e6a1e895f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019c4eb7-8266-7bbf-baa5-215bd6c0ec34" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c4eb7-8266-71ec-8528-a908cead5892" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019c4eb7-8266-7bbf-baa5-215bd6c0ec34" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019c4eb7-8266-7ea7-aedb-e9cd6ff24ae7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c4eb7-8266-71ec-8528-a908cead5892" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019c4eb7-8266-7ea7-aedb-e9cd6ff24ae7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodFairValue_019c4eb7-8266-7fca-85ca-438e8e940dac" xlink:href="aos-20260331.xsd#aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c4eb7-8266-71ec-8528-a908cead5892" xlink:to="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodFairValue_019c4eb7-8266-7fca-85ca-438e8e940dac" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019c4eb7-8266-7619-a36d-a258c06b9b98" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c4eb7-8266-71ec-8528-a908cead5892" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019c4eb7-8266-7619-a36d-a258c06b9b98" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardPotentialPayoutPercentOfTargetAwards_019c4eb7-8266-7d8c-8b47-420ac7f9bed8" xlink:href="aos-20260331.xsd#aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardPotentialPayoutPercentOfTargetAwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c4eb7-8266-71ec-8528-a908cead5892" xlink:to="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardPotentialPayoutPercentOfTargetAwards_019c4eb7-8266-7d8c-8b47-420ac7f9bed8" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/ShareBasedCompensationScheduleofShareUnitActivityUnderPlanDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#ShareBasedCompensationScheduleofShareUnitActivityUnderPlanDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/ShareBasedCompensationScheduleofShareUnitActivityUnderPlanDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c4eb7-8266-70ff-87b8-e2a14e790d74" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019c4eb7-8266-7684-b47d-fb6da8a7629d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c4eb7-8266-70ff-87b8-e2a14e790d74" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019c4eb7-8266-7684-b47d-fb6da8a7629d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019c4eb7-8266-7acf-930b-b6fec73f5165" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019c4eb7-8266-7684-b47d-fb6da8a7629d" xlink:to="loc_us-gaap_AwardTypeAxis_019c4eb7-8266-7acf-930b-b6fec73f5165" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c4eb7-8266-7acf-930b-b6fec73f5165_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019c4eb7-8266-7acf-930b-b6fec73f5165" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c4eb7-8266-7acf-930b-b6fec73f5165_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c4eb7-8266-71ca-9c82-fe8158c0f485" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019c4eb7-8266-7acf-930b-b6fec73f5165" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c4eb7-8266-71ca-9c82-fe8158c0f485" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019c4eb7-8266-7ff7-8f3b-1008c510644b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c4eb7-8266-71ca-9c82-fe8158c0f485" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019c4eb7-8266-7ff7-8f3b-1008c510644b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019c4eb7-8266-74b7-addc-4f641b881574" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c4eb7-8266-70ff-87b8-e2a14e790d74" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019c4eb7-8266-74b7-addc-4f641b881574" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019c4eb7-8266-7ac6-99fe-d3012323a712" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019c4eb7-8266-74b7-addc-4f641b881574" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019c4eb7-8266-7ac6-99fe-d3012323a712" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019c4eb7-8266-7b63-9217-c38fd627d3aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019c4eb7-8266-74b7-addc-4f641b881574" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019c4eb7-8266-7b63-9217-c38fd627d3aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019c4eb7-8266-777a-ac78-6be89a1283ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019c4eb7-8266-74b7-addc-4f641b881574" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019c4eb7-8266-777a-ac78-6be89a1283ba" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019c4eb7-8266-7248-a7d7-c45df486f6b1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsNonvestedWeightedAverageExercisePriceRollForward_019c4eb7-8266-760d-89a7-b07a2e19a1d0" xlink:href="aos-20260331.xsd#aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsNonvestedWeightedAverageExercisePriceRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c4eb7-8266-70ff-87b8-e2a14e790d74" xlink:to="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsNonvestedWeightedAverageExercisePriceRollForward_019c4eb7-8266-760d-89a7-b07a2e19a1d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019c4eb7-8266-7862-8721-996b6b392665" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsNonvestedWeightedAverageExercisePriceRollForward_019c4eb7-8266-760d-89a7-b07a2e19a1d0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019c4eb7-8266-7862-8721-996b6b392665" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019c4eb7-8266-7f6c-870d-adc4bc2b8cc2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsNonvestedWeightedAverageExercisePriceRollForward_019c4eb7-8266-760d-89a7-b07a2e19a1d0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019c4eb7-8266-7f6c-870d-adc4bc2b8cc2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019c4eb7-8266-7ee9-892b-83cf3e93ee29" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsNonvestedWeightedAverageExercisePriceRollForward_019c4eb7-8266-760d-89a7-b07a2e19a1d0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019c4eb7-8266-7ee9-892b-83cf3e93ee29" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019c4eb7-8266-76ff-90eb-f4f9c8d9b666" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/ShareBasedCompensationScheduleofPerformanceStockUnitActivityDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#ShareBasedCompensationScheduleofPerformanceStockUnitActivityDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/ShareBasedCompensationScheduleofPerformanceStockUnitActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c4eb7-8266-70d1-9a82-38e70477d81e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019c4eb7-8266-7222-80e9-f35eb5ed5a1a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c4eb7-8266-70d1-9a82-38e70477d81e" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019c4eb7-8266-7222-80e9-f35eb5ed5a1a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019c4eb7-8266-7e9b-8dbb-a0094bb77896" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019c4eb7-8266-7222-80e9-f35eb5ed5a1a" xlink:to="loc_us-gaap_AwardTypeAxis_019c4eb7-8266-7e9b-8dbb-a0094bb77896" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c4eb7-8266-7e9b-8dbb-a0094bb77896_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019c4eb7-8266-7e9b-8dbb-a0094bb77896" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c4eb7-8266-7e9b-8dbb-a0094bb77896_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c4eb7-8266-7154-94a9-46a1f61b7285" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019c4eb7-8266-7e9b-8dbb-a0094bb77896" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c4eb7-8266-7154-94a9-46a1f61b7285" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_019c4eb7-8266-7d05-906d-62e67aaf2da7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c4eb7-8266-7154-94a9-46a1f61b7285" xlink:to="loc_us-gaap_PerformanceSharesMember_019c4eb7-8266-7d05-906d-62e67aaf2da7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019c4eb7-8266-7e88-bd59-1893b0a3bb67" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c4eb7-8266-70d1-9a82-38e70477d81e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019c4eb7-8266-7e88-bd59-1893b0a3bb67" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019c4eb7-8266-70a1-9004-7fb3de72cfa4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019c4eb7-8266-7e88-bd59-1893b0a3bb67" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019c4eb7-8266-70a1-9004-7fb3de72cfa4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019c4eb7-8266-781a-be56-eb1366701d1d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019c4eb7-8266-7e88-bd59-1893b0a3bb67" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019c4eb7-8266-781a-be56-eb1366701d1d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019d86b4-27ba-7c10-bdcc-9094922b1957" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019c4eb7-8266-7e88-bd59-1893b0a3bb67" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019d86b4-27ba-7c10-bdcc-9094922b1957" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustments_019d86b4-27ba-7a2a-966a-96acb71dd190" xlink:href="aos-20260331.xsd#aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019c4eb7-8266-7e88-bd59-1893b0a3bb67" xlink:to="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustments_019d86b4-27ba-7a2a-966a-96acb71dd190" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019c4eb7-8266-721d-96ce-b84431dbf131" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsNonvestedWeightedAverageExercisePriceRollForward_019c4eb7-8266-785b-9aa1-ffcb49ccf123" xlink:href="aos-20260331.xsd#aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsNonvestedWeightedAverageExercisePriceRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c4eb7-8266-70d1-9a82-38e70477d81e" xlink:to="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsNonvestedWeightedAverageExercisePriceRollForward_019c4eb7-8266-785b-9aa1-ffcb49ccf123" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019c4eb7-8266-74d4-aed7-564b8171c7e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsNonvestedWeightedAverageExercisePriceRollForward_019c4eb7-8266-785b-9aa1-ffcb49ccf123" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019c4eb7-8266-74d4-aed7-564b8171c7e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019c4eb7-8266-765e-9ae1-963c11b778c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsNonvestedWeightedAverageExercisePriceRollForward_019c4eb7-8266-785b-9aa1-ffcb49ccf123" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019c4eb7-8266-765e-9ae1-963c11b778c8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019d86b4-27ba-7416-9a2c-c02e66baf230" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsNonvestedWeightedAverageExercisePriceRollForward_019c4eb7-8266-785b-9aa1-ffcb49ccf123" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019d86b4-27ba-7416-9a2c-c02e66baf230" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustmentsWeightedAverageGrantDateFairValue_019d86b4-27ba-7528-9627-36a6146946df" xlink:href="aos-20260331.xsd#aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustmentsWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsNonvestedWeightedAverageExercisePriceRollForward_019c4eb7-8266-785b-9aa1-ffcb49ccf123" xlink:to="loc_aos_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustmentsWeightedAverageGrantDateFairValue_019d86b4-27ba-7528-9627-36a6146946df" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019c4eb7-8266-77e0-9c33-6bedc371673b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/SegmentResultsScheduleofReportableSegmentDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#SegmentResultsScheduleofReportableSegmentDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/SegmentResultsScheduleofReportableSegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019c4eb7-8266-73d2-b6c2-497603216dd0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019c4eb7-8266-73de-8e7d-d6ab07de72b1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c4eb7-8266-73d2-b6c2-497603216dd0" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019c4eb7-8266-73de-8e7d-d6ab07de72b1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019c4eb7-8266-7e42-acbd-af0a21ec3712" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019c4eb7-8266-73de-8e7d-d6ab07de72b1" xlink:to="loc_srt_ConsolidationItemsAxis_019c4eb7-8266-7e42-acbd-af0a21ec3712" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7e42-acbd-af0a21ec3712_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019c4eb7-8266-7e42-acbd-af0a21ec3712" xlink:to="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7e42-acbd-af0a21ec3712_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7c31-b98f-f1a624feadfd" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019c4eb7-8266-7e42-acbd-af0a21ec3712" xlink:to="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7c31-b98f-f1a624feadfd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntersegmentEliminationMember_019c4eb7-8266-7e2e-8fb1-55a24c61ea22" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IntersegmentEliminationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7c31-b98f-f1a624feadfd" xlink:to="loc_us-gaap_IntersegmentEliminationMember_019c4eb7-8266-7e2e-8fb1-55a24c61ea22" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019c4eb7-8266-7f88-828b-39526d33b259" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7c31-b98f-f1a624feadfd" xlink:to="loc_us-gaap_OperatingSegmentsMember_019c4eb7-8266-7f88-828b-39526d33b259" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_019c4eb7-8266-7ac9-ab0e-ffe9c378b3a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7c31-b98f-f1a624feadfd" xlink:to="loc_us-gaap_CorporateNonSegmentMember_019c4eb7-8266-7ac9-ab0e-ffe9c378b3a1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019c4eb7-8266-71ea-864e-6b4cee3d89ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019c4eb7-8266-73de-8e7d-d6ab07de72b1" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019c4eb7-8266-71ea-864e-6b4cee3d89ee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c4eb7-8266-71ea-864e-6b4cee3d89ee_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c4eb7-8266-71ea-864e-6b4cee3d89ee" xlink:to="loc_us-gaap_SegmentDomain_019c4eb7-8266-71ea-864e-6b4cee3d89ee_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c4eb7-8266-7cc3-9507-cefdd7ff3f7a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c4eb7-8266-71ea-864e-6b4cee3d89ee" xlink:to="loc_us-gaap_SegmentDomain_019c4eb7-8266-7cc3-9507-cefdd7ff3f7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_ReportableSegmentsMember_019c4eb7-8266-76e3-88b7-1f176f68a21c" xlink:href="aos-20260331.xsd#aos_ReportableSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019c4eb7-8266-7cc3-9507-cefdd7ff3f7a" xlink:to="loc_aos_ReportableSegmentsMember_019c4eb7-8266-76e3-88b7-1f176f68a21c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_NorthAmericaSegmentMember_019c4eb7-8266-71ca-bee5-fecb373d38f8" xlink:href="aos-20260331.xsd#aos_NorthAmericaSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aos_ReportableSegmentsMember_019c4eb7-8266-76e3-88b7-1f176f68a21c" xlink:to="loc_aos_NorthAmericaSegmentMember_019c4eb7-8266-71ca-bee5-fecb373d38f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_RestOfWorldMember_019c4eb7-8266-7f4f-bd8a-e11fff15b09a" xlink:href="aos-20260331.xsd#aos_RestOfWorldMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aos_ReportableSegmentsMember_019c4eb7-8266-76e3-88b7-1f176f68a21c" xlink:to="loc_aos_RestOfWorldMember_019c4eb7-8266-7f4f-bd8a-e11fff15b09a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c4eb7-8266-7bf2-aa0d-0f3b8872a389" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c4eb7-8266-73d2-b6c2-497603216dd0" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c4eb7-8266-7bf2-aa0d-0f3b8872a389" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_019c4eb7-8266-7c58-b556-10495a5833ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c4eb7-8266-73d2-b6c2-497603216dd0" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_019c4eb7-8266-7c58-b556-10495a5833ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_019c4eb7-8266-73fb-b338-51e4ed730fce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c4eb7-8266-73d2-b6c2-497603216dd0" xlink:to="loc_us-gaap_GrossProfit_019c4eb7-8266-73fb-b338-51e4ed730fce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019c4eb7-8266-7894-ae23-66724037404d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c4eb7-8266-73d2-b6c2-497603216dd0" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019c4eb7-8266-7894-ae23-66724037404d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019c4eb7-8266-76fe-937e-9b32d6723696" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c4eb7-8266-73d2-b6c2-497603216dd0" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019c4eb7-8266-76fe-937e-9b32d6723696" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019c4eb7-8266-7888-ad91-56affe316c0a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c4eb7-8266-73d2-b6c2-497603216dd0" xlink:to="loc_us-gaap_OperatingIncomeLoss_019c4eb7-8266-7888-ad91-56affe316c0a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_019c4eb7-8266-7e42-afe5-ce28e93cc057" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c4eb7-8266-73d2-b6c2-497603216dd0" xlink:to="loc_us-gaap_InterestExpense_019c4eb7-8266-7e42-afe5-ce28e93cc057" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019c4eb7-8266-73b1-af94-8f00055e3886" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c4eb7-8266-73d2-b6c2-497603216dd0" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019c4eb7-8266-73b1-af94-8f00055e3886" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/SegmentResultsScheduleofAssetsDepreciationandCapitalExpenditurebySegmentDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#SegmentResultsScheduleofAssetsDepreciationandCapitalExpenditurebySegmentDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/SegmentResultsScheduleofAssetsDepreciationandCapitalExpenditurebySegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019c4eb7-8266-7bba-9c53-c4df2e0214b8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019c4eb7-8266-71b8-9ea3-16f66331e255" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c4eb7-8266-7bba-9c53-c4df2e0214b8" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019c4eb7-8266-71b8-9ea3-16f66331e255" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019c4eb7-8266-7e88-b213-db6af1f9a4e5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019c4eb7-8266-71b8-9ea3-16f66331e255" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019c4eb7-8266-7e88-b213-db6af1f9a4e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c4eb7-8266-7e88-b213-db6af1f9a4e5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c4eb7-8266-7e88-b213-db6af1f9a4e5" xlink:to="loc_us-gaap_SegmentDomain_019c4eb7-8266-7e88-b213-db6af1f9a4e5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c4eb7-8266-763b-8397-e6474fc15116" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c4eb7-8266-7e88-b213-db6af1f9a4e5" xlink:to="loc_us-gaap_SegmentDomain_019c4eb7-8266-763b-8397-e6474fc15116" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_NorthAmericaSegmentMember_019c4eb7-8266-7ffb-ab8e-4c1fb6e44141" xlink:href="aos-20260331.xsd#aos_NorthAmericaSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019c4eb7-8266-763b-8397-e6474fc15116" xlink:to="loc_aos_NorthAmericaSegmentMember_019c4eb7-8266-7ffb-ab8e-4c1fb6e44141" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_RestOfWorldMember_019c4eb7-8266-7d29-b1f9-91b00259215e" xlink:href="aos-20260331.xsd#aos_RestOfWorldMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019c4eb7-8266-763b-8397-e6474fc15116" xlink:to="loc_aos_RestOfWorldMember_019c4eb7-8266-7d29-b1f9-91b00259215e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019c4eb7-8266-7239-9290-00fd10094c95" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019c4eb7-8266-71b8-9ea3-16f66331e255" xlink:to="loc_srt_ConsolidationItemsAxis_019c4eb7-8266-7239-9290-00fd10094c95" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7239-9290-00fd10094c95_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019c4eb7-8266-7239-9290-00fd10094c95" xlink:to="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7239-9290-00fd10094c95_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7244-b8c8-2228e15e38a8" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019c4eb7-8266-7239-9290-00fd10094c95" xlink:to="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7244-b8c8-2228e15e38a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019c4eb7-8266-7159-a8ef-c36d845ed6d5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7244-b8c8-2228e15e38a8" xlink:to="loc_us-gaap_OperatingSegmentsMember_019c4eb7-8266-7159-a8ef-c36d845ed6d5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_019c4eb7-8266-7aa4-b163-99d79b6f401a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019c4eb7-8266-7244-b8c8-2228e15e38a8" xlink:to="loc_us-gaap_CorporateNonSegmentMember_019c4eb7-8266-7aa4-b163-99d79b6f401a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019c4eb7-8266-7eb8-9181-202d84d795dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c4eb7-8266-7bba-9c53-c4df2e0214b8" xlink:to="loc_us-gaap_Assets_019c4eb7-8266-7eb8-9181-202d84d795dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_019c4eb7-8266-7bf5-a9e5-c0268ef28d42" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c4eb7-8266-7bba-9c53-c4df2e0214b8" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_019c4eb7-8266-7bf5-a9e5-c0268ef28d42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireProductiveAssets_019c4eb7-8266-72b6-8c9b-4dabe412baca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireProductiveAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c4eb7-8266-7bba-9c53-c4df2e0214b8" xlink:to="loc_us-gaap_PaymentsToAcquireProductiveAssets_019c4eb7-8266-72b6-8c9b-4dabe412baca" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/FairValueMeasurementsDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#FairValueMeasurementsDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/FairValueMeasurementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c4eb7-8266-731b-81f8-2a5308b93eb5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c4eb7-8266-70b4-b6d8-311639e5bd5b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c4eb7-8266-731b-81f8-2a5308b93eb5" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c4eb7-8266-70b4-b6d8-311639e5bd5b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c4eb7-8266-7146-9eb0-ab6ad259cc89" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c4eb7-8266-70b4-b6d8-311639e5bd5b" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c4eb7-8266-7146-9eb0-ab6ad259cc89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c4eb7-8266-7146-9eb0-ab6ad259cc89_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c4eb7-8266-7146-9eb0-ab6ad259cc89" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c4eb7-8266-7146-9eb0-ab6ad259cc89_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c4eb7-8266-7337-b2af-f1511b9e1725" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c4eb7-8266-7146-9eb0-ab6ad259cc89" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c4eb7-8266-7337-b2af-f1511b9e1725" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019c4eb7-8266-700b-9fee-419e9e8ab833" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c4eb7-8266-7337-b2af-f1511b9e1725" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019c4eb7-8266-700b-9fee-419e9e8ab833" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019c4eb7-8266-7871-a237-aa34b7bf05c0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c4eb7-8266-7337-b2af-f1511b9e1725" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019c4eb7-8266-7871-a237-aa34b7bf05c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetAssetLiability_019c4eb7-8266-7975-ab22-5ece9c82f63c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueNetAssetLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c4eb7-8266-731b-81f8-2a5308b93eb5" xlink:to="loc_us-gaap_FairValueNetAssetLiability_019c4eb7-8266-7975-ab22-5ece9c82f63c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/DerivativeInstrumentsNarrativeDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#DerivativeInstrumentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/DerivativeInstrumentsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingActivityGainsAndLossesLineItems_019c4eb7-8267-7de1-a655-dca2fca6ea52" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradingActivityGainsAndLossesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingActivitiesGainLossByTypeTable_019c4eb7-8266-7a34-93a5-23774c82fb7d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradingActivitiesGainLossByTypeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_TradingActivityGainsAndLossesLineItems_019c4eb7-8267-7de1-a655-dca2fca6ea52" xlink:to="loc_us-gaap_TradingActivitiesGainLossByTypeTable_019c4eb7-8266-7a34-93a5-23774c82fb7d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingActivityByTypeAxis_019cd228-2e4d-7e82-a888-b4c50c18a476" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradingActivityByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TradingActivitiesGainLossByTypeTable_019c4eb7-8266-7a34-93a5-23774c82fb7d" xlink:to="loc_us-gaap_TradingActivityByTypeAxis_019cd228-2e4d-7e82-a888-b4c50c18a476" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingActivityByTypeDomain_019cd228-2e4d-7e82-a888-b4c50c18a476_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradingActivityByTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TradingActivityByTypeAxis_019cd228-2e4d-7e82-a888-b4c50c18a476" xlink:to="loc_us-gaap_TradingActivityByTypeDomain_019cd228-2e4d-7e82-a888-b4c50c18a476_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingActivityByTypeDomain_019cd228-2e4d-7f6b-9d3b-ea63c4696b85" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradingActivityByTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TradingActivityByTypeAxis_019cd228-2e4d-7e82-a888-b4c50c18a476" xlink:to="loc_us-gaap_TradingActivityByTypeDomain_019cd228-2e4d-7f6b-9d3b-ea63c4696b85" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_CommodityFuturesContractsMember_019cd228-2e4d-78f6-ba4d-1b72acb0debc" xlink:href="aos-20260331.xsd#aos_CommodityFuturesContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TradingActivityByTypeDomain_019cd228-2e4d-7f6b-9d3b-ea63c4696b85" xlink:to="loc_aos_CommodityFuturesContractsMember_019cd228-2e4d-78f6-ba4d-1b72acb0debc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019c4eb7-8266-7226-aac0-bc5e557b1a10" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TradingActivitiesGainLossByTypeTable_019c4eb7-8266-7a34-93a5-23774c82fb7d" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019c4eb7-8266-7226-aac0-bc5e557b1a10" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8266-7226-aac0-bc5e557b1a10_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c4eb7-8266-7226-aac0-bc5e557b1a10" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8266-7226-aac0-bc5e557b1a10_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8266-7a50-8627-04b37795ccec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c4eb7-8266-7226-aac0-bc5e557b1a10" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8266-7a50-8627-04b37795ccec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_019c4eb7-8266-7f47-8613-1f1861d90f20" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8266-7a50-8627-04b37795ccec" xlink:to="loc_us-gaap_ForeignExchangeContractMember_019c4eb7-8266-7f47-8613-1f1861d90f20" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019c4eb7-8266-7a78-87d3-85440d88411c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8266-7a50-8627-04b37795ccec" xlink:to="loc_us-gaap_InterestRateSwapMember_019c4eb7-8266-7a78-87d3-85440d88411c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_019c4eb7-8266-7a7a-a4a6-b2c2d4b578e2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8266-7a50-8627-04b37795ccec" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_019c4eb7-8266-7a7a-a4a6-b2c2d4b578e2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019c4eb7-8266-797c-bf42-a5afbc5a45e9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TradingActivitiesGainLossByTypeTable_019c4eb7-8266-7a34-93a5-23774c82fb7d" xlink:to="loc_us-gaap_HedgingDesignationAxis_019c4eb7-8266-797c-bf42-a5afbc5a45e9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019c4eb7-8266-797c-bf42-a5afbc5a45e9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019c4eb7-8266-797c-bf42-a5afbc5a45e9" xlink:to="loc_us-gaap_HedgingDesignationDomain_019c4eb7-8266-797c-bf42-a5afbc5a45e9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019c4eb7-8266-7671-a44d-6554c1621908" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019c4eb7-8266-797c-bf42-a5afbc5a45e9" xlink:to="loc_us-gaap_HedgingDesignationDomain_019c4eb7-8266-7671-a44d-6554c1621908" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019c4eb7-8266-7c96-b896-525a9ae57476" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019c4eb7-8266-7671-a44d-6554c1621908" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019c4eb7-8266-7c96-b896-525a9ae57476" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019c4eb7-8267-7201-bb99-8114139c1d06" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TradingActivitiesGainLossByTypeTable_019c4eb7-8266-7a34-93a5-23774c82fb7d" xlink:to="loc_srt_StatementGeographicalAxis_019c4eb7-8267-7201-bb99-8114139c1d06" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019c4eb7-8267-7201-bb99-8114139c1d06_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019c4eb7-8267-7201-bb99-8114139c1d06" xlink:to="loc_srt_SegmentGeographicalDomain_019c4eb7-8267-7201-bb99-8114139c1d06_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019c4eb7-8267-7d6f-99ab-b8d8ea2bf8c2" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019c4eb7-8267-7201-bb99-8114139c1d06" xlink:to="loc_srt_SegmentGeographicalDomain_019c4eb7-8267-7d6f-99ab-b8d8ea2bf8c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_019c4eb7-8267-783a-81ff-7b983f6fe1d5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019c4eb7-8267-7d6f-99ab-b8d8ea2bf8c2" xlink:to="loc_us-gaap_NonUsMember_019c4eb7-8267-783a-81ff-7b983f6fe1d5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c4eb7-8267-7dc8-ab19-6c621efce905" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TradingActivitiesGainLossByTypeTable_019c4eb7-8266-7a34-93a5-23774c82fb7d" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c4eb7-8267-7dc8-ab19-6c621efce905" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019c4eb7-8267-7dc8-ab19-6c621efce905_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c4eb7-8267-7dc8-ab19-6c621efce905" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019c4eb7-8267-7dc8-ab19-6c621efce905_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019c4eb7-8267-74c4-ab79-604dba7e9b20" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c4eb7-8267-7dc8-ab19-6c621efce905" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019c4eb7-8267-74c4-ab79-604dba7e9b20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentHedgingMember_019c4eb7-8267-797d-83b7-062fcb12c5e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetInvestmentHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_019c4eb7-8267-74c4-ab79-604dba7e9b20" xlink:to="loc_us-gaap_NetInvestmentHedgingMember_019c4eb7-8267-797d-83b7-062fcb12c5e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_aos_ReclassificationPeriodForEffectivePortionOfContract_019cd228-2e4d-7248-8090-f02db10f43ea" xlink:href="aos-20260331.xsd#aos_ReclassificationPeriodForEffectivePortionOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TradingActivityGainsAndLossesLineItems_019c4eb7-8267-7de1-a655-dca2fca6ea52" xlink:to="loc_aos_ReclassificationPeriodForEffectivePortionOfContract_019cd228-2e4d-7248-8090-f02db10f43ea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019c4eb7-8267-7c8c-b038-6a34ccd9ea99" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TradingActivityGainsAndLossesLineItems_019c4eb7-8267-7de1-a655-dca2fca6ea52" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019c4eb7-8267-7c8c-b038-6a34ccd9ea99" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_019c4eb7-8267-743c-99af-b697216fe32b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TradingActivityGainsAndLossesLineItems_019c4eb7-8267-7de1-a655-dca2fca6ea52" xlink:to="loc_us-gaap_DerivativeNotionalAmount_019c4eb7-8267-743c-99af-b697216fe32b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFixedInterestRate_019c4eb7-8267-75da-9669-ff9e4e8a0a51" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFixedInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TradingActivityGainsAndLossesLineItems_019c4eb7-8267-7de1-a655-dca2fca6ea52" xlink:to="loc_us-gaap_DerivativeFixedInterestRate_019c4eb7-8267-75da-9669-ff9e4e8a0a51" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateDerivativeLiabilitiesAtFairValue_019c4eb7-8267-7268-bae3-d2b2f0104267" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateDerivativeLiabilitiesAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TradingActivityGainsAndLossesLineItems_019c4eb7-8267-7de1-a655-dca2fca6ea52" xlink:to="loc_us-gaap_InterestRateDerivativeLiabilitiesAtFairValue_019c4eb7-8267-7268-bae3-d2b2f0104267" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_019c4eb7-8267-7548-b797-62c744c27634" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TradingActivityGainsAndLossesLineItems_019c4eb7-8267-7de1-a655-dca2fca6ea52" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_019c4eb7-8267-7548-b797-62c744c27634" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/DerivativeInstrumentsScheduleofCurrencyofForeignCurrencyForwardContractsDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#DerivativeInstrumentsScheduleofCurrencyofForeignCurrencyForwardContractsDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/DerivativeInstrumentsScheduleofCurrencyofForeignCurrencyForwardContractsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019c4eb7-8267-7ffd-84ae-a60e6457b26b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_019c4eb7-8267-705f-975c-c4be71005461" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019c4eb7-8267-7ffd-84ae-a60e6457b26b" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_019c4eb7-8267-705f-975c-c4be71005461" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019c4eb7-8267-731d-80cf-a00f4e870904" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_019c4eb7-8267-705f-975c-c4be71005461" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019c4eb7-8267-731d-80cf-a00f4e870904" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8267-731d-80cf-a00f4e870904_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c4eb7-8267-731d-80cf-a00f4e870904" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8267-731d-80cf-a00f4e870904_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8267-7f6b-aa74-2be41a441bbe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c4eb7-8267-731d-80cf-a00f4e870904" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8267-7f6b-aa74-2be41a441bbe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_019c4eb7-8267-7d9a-bd59-b2340b55a736" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8267-7f6b-aa74-2be41a441bbe" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_019c4eb7-8267-7d9a-bd59-b2340b55a736" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019c4eb7-8267-7294-b95e-471b23a827f1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_019c4eb7-8267-705f-975c-c4be71005461" xlink:to="loc_us-gaap_HedgingDesignationAxis_019c4eb7-8267-7294-b95e-471b23a827f1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019c4eb7-8267-7294-b95e-471b23a827f1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019c4eb7-8267-7294-b95e-471b23a827f1" xlink:to="loc_us-gaap_HedgingDesignationDomain_019c4eb7-8267-7294-b95e-471b23a827f1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019c4eb7-8267-7936-9509-4958e0fa562f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019c4eb7-8267-7294-b95e-471b23a827f1" xlink:to="loc_us-gaap_HedgingDesignationDomain_019c4eb7-8267-7936-9509-4958e0fa562f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019c4eb7-8267-70d3-b678-9f3c3bc760a5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019c4eb7-8267-7936-9509-4958e0fa562f" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019c4eb7-8267-70d3-b678-9f3c3bc760a5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c4eb7-8267-7877-b9db-93ccd3c2c58c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_019c4eb7-8267-705f-975c-c4be71005461" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c4eb7-8267-7877-b9db-93ccd3c2c58c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019c4eb7-8267-7877-b9db-93ccd3c2c58c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c4eb7-8267-7877-b9db-93ccd3c2c58c" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019c4eb7-8267-7877-b9db-93ccd3c2c58c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019c4eb7-8267-7d6c-8052-58656dca238a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c4eb7-8267-7877-b9db-93ccd3c2c58c" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019c4eb7-8267-7d6c-8052-58656dca238a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_019c4eb7-8267-7bf1-8c8a-a1f3dfbf11fe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashFlowHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_019c4eb7-8267-7d6c-8052-58656dca238a" xlink:to="loc_us-gaap_CashFlowHedgingMember_019c4eb7-8267-7bf1-8c8a-a1f3dfbf11fe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PositionAxis_019c4eb7-8267-7b7d-abbd-d306582b3f17" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PositionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_019c4eb7-8267-705f-975c-c4be71005461" xlink:to="loc_us-gaap_PositionAxis_019c4eb7-8267-7b7d-abbd-d306582b3f17" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PositionDomain_019c4eb7-8267-7b7d-abbd-d306582b3f17_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PositionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PositionAxis_019c4eb7-8267-7b7d-abbd-d306582b3f17" xlink:to="loc_us-gaap_PositionDomain_019c4eb7-8267-7b7d-abbd-d306582b3f17_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PositionDomain_019c4eb7-8267-775a-bb1f-a2d4ba878024" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PositionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PositionAxis_019c4eb7-8267-7b7d-abbd-d306582b3f17" xlink:to="loc_us-gaap_PositionDomain_019c4eb7-8267-775a-bb1f-a2d4ba878024" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongMember_019c4eb7-8267-7ca4-b52a-316fc5cea389" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PositionDomain_019c4eb7-8267-775a-bb1f-a2d4ba878024" xlink:to="loc_us-gaap_LongMember_019c4eb7-8267-7ca4-b52a-316fc5cea389" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortMember_019c4eb7-8267-75be-8353-fb1dd9317359" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PositionDomain_019c4eb7-8267-775a-bb1f-a2d4ba878024" xlink:to="loc_us-gaap_ShortMember_019c4eb7-8267-75be-8353-fb1dd9317359" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CurrencyAxis_019c4eb7-8267-799c-9dcb-12b3c8145795" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CurrencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_019c4eb7-8267-705f-975c-c4be71005461" xlink:to="loc_srt_CurrencyAxis_019c4eb7-8267-799c-9dcb-12b3c8145795" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_019c4eb7-8267-799c-9dcb-12b3c8145795_default" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CurrencyAxis_019c4eb7-8267-799c-9dcb-12b3c8145795" xlink:to="loc_currency_AllCurrenciesDomain_019c4eb7-8267-799c-9dcb-12b3c8145795_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_019c4eb7-8267-78a0-88e7-acb49b908e7c" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CurrencyAxis_019c4eb7-8267-799c-9dcb-12b3c8145795" xlink:to="loc_currency_AllCurrenciesDomain_019c4eb7-8267-78a0-88e7-acb49b908e7c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_CAD_019c4eb7-8267-7ef8-99f9-fb38ad8e194e" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_CAD"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_019c4eb7-8267-78a0-88e7-acb49b908e7c" xlink:to="loc_currency_CAD_019c4eb7-8267-7ef8-99f9-fb38ad8e194e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_EUR_019c4eb7-8267-7e0a-8525-e476e0a4795f" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_EUR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_019c4eb7-8267-78a0-88e7-acb49b908e7c" xlink:to="loc_currency_EUR_019c4eb7-8267-7e0a-8525-e476e0a4795f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_MXN_019c4eb7-8267-71b5-a53a-3347c0feace3" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_MXN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_019c4eb7-8267-78a0-88e7-acb49b908e7c" xlink:to="loc_currency_MXN_019c4eb7-8267-71b5-a53a-3347c0feace3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_019c4eb7-8267-7c41-bfc6-dde07224a92e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019c4eb7-8267-7ffd-84ae-a60e6457b26b" xlink:to="loc_us-gaap_DerivativeNotionalAmount_019c4eb7-8267-7c41-bfc6-dde07224a92e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/DerivativeInstrumentsScheduleofEffectofCashFlowHedgesonConsolidatedStatementofEarningsDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#DerivativeInstrumentsScheduleofEffectofCashFlowHedgesonConsolidatedStatementofEarningsDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/DerivativeInstrumentsScheduleofEffectofCashFlowHedgesonConsolidatedStatementofEarningsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_019c4eb7-8267-70dc-8399-53a59aa229f8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_019c4eb7-8267-7cd7-ab1b-40754787b580" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_019c4eb7-8267-70dc-8399-53a59aa229f8" xlink:to="loc_us-gaap_DerivativeTable_019c4eb7-8267-7cd7-ab1b-40754787b580" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019c4eb7-8267-7d34-88da-3424278003ed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019c4eb7-8267-7cd7-ab1b-40754787b580" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019c4eb7-8267-7d34-88da-3424278003ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8267-7d34-88da-3424278003ed_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c4eb7-8267-7d34-88da-3424278003ed" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8267-7d34-88da-3424278003ed_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8267-7e3b-a42d-fe3019ff288a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c4eb7-8267-7d34-88da-3424278003ed" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8267-7e3b-a42d-fe3019ff288a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_019c4eb7-8267-7c1c-ab51-75fc8166df5f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8267-7e3b-a42d-fe3019ff288a" xlink:to="loc_us-gaap_ForeignExchangeContractMember_019c4eb7-8267-7c1c-ab51-75fc8166df5f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019c4eb7-8267-756b-b421-02203bcabda9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c4eb7-8267-7e3b-a42d-fe3019ff288a" xlink:to="loc_us-gaap_InterestRateSwapMember_019c4eb7-8267-756b-b421-02203bcabda9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax_019c4eb7-8267-7191-8887-586ebae92b02" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019c4eb7-8267-70dc-8399-53a59aa229f8" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax_019c4eb7-8267-7191-8887-586ebae92b02" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax_019c4eb7-8267-714d-8de9-cbf1caecca44" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019c4eb7-8267-70dc-8399-53a59aa229f8" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax_019c4eb7-8267-714d-8de9-cbf1caecca44" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/IncomeTaxesDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#IncomeTaxesDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/IncomeTaxesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxContingencyLineItems_019c4eb7-8267-7b16-af41-1b0429f66d87" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxContingencyLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxContingencyTable_019c4eb7-8267-7b41-9e21-7a34f5c48c96" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxContingencyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_019c4eb7-8267-7b16-af41-1b0429f66d87" xlink:to="loc_us-gaap_IncomeTaxContingencyTable_019c4eb7-8267-7b41-9e21-7a34f5c48c96" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019c4eb7-8267-76d7-adff-3760c124c252" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxContingencyTable_019c4eb7-8267-7b41-9e21-7a34f5c48c96" xlink:to="loc_srt_RangeAxis_019c4eb7-8267-76d7-adff-3760c124c252" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019c4eb7-8267-76d7-adff-3760c124c252_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019c4eb7-8267-76d7-adff-3760c124c252" xlink:to="loc_srt_RangeMember_019c4eb7-8267-76d7-adff-3760c124c252_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019c4eb7-8267-7bda-ac22-7eea9949412d" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019c4eb7-8267-76d7-adff-3760c124c252" xlink:to="loc_srt_RangeMember_019c4eb7-8267-7bda-ac22-7eea9949412d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019c4eb7-8267-75e3-8134-ef5208bd879f" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019c4eb7-8267-7bda-ac22-7eea9949412d" xlink:to="loc_srt_MinimumMember_019c4eb7-8267-75e3-8134-ef5208bd879f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019c4eb7-8267-7eb7-8cf7-ca98f7124b54" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019c4eb7-8267-7bda-ac22-7eea9949412d" xlink:to="loc_srt_MaximumMember_019c4eb7-8267-7eb7-8cf7-ca98f7124b54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_019c4eb7-8267-719d-8e2f-12f7ee770afa" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxContingencyTable_019c4eb7-8267-7b41-9e21-7a34f5c48c96" xlink:to="loc_srt_StatementScenarioAxis_019c4eb7-8267-719d-8e2f-12f7ee770afa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019c4eb7-8267-719d-8e2f-12f7ee770afa_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_019c4eb7-8267-719d-8e2f-12f7ee770afa" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019c4eb7-8267-719d-8e2f-12f7ee770afa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019c4eb7-8267-79cb-85a7-5ac692eb3407" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_019c4eb7-8267-719d-8e2f-12f7ee770afa" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019c4eb7-8267-79cb-85a7-5ac692eb3407" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_019c4eb7-8267-7e51-baea-e0aaaeb36811" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_019c4eb7-8267-79cb-85a7-5ac692eb3407" xlink:to="loc_srt_ScenarioForecastMember_019c4eb7-8267-7e51-baea-e0aaaeb36811" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c4eb7-8267-7c0d-b681-89bfffcce0b3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_019c4eb7-8267-7b16-af41-1b0429f66d87" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c4eb7-8267-7c0d-b681-89bfffcce0b3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecognizedTaxBenefits_019c4eb7-8267-7f02-921f-50106f119328" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnrecognizedTaxBenefits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_019c4eb7-8267-7b16-af41-1b0429f66d87" xlink:to="loc_us-gaap_UnrecognizedTaxBenefits_019c4eb7-8267-7f02-921f-50106f119328" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate_019c4eb7-8267-73fc-91f8-bb14570ad3e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_019c4eb7-8267-7b16-af41-1b0429f66d87" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate_019c4eb7-8267-73fc-91f8-bb14570ad3e6" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/ChangesinAccumulatedOtherComprehensiveLossbyComponentDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#ChangesinAccumulatedOtherComprehensiveLossbyComponentDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/ChangesinAccumulatedOtherComprehensiveLossbyComponentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019c4eb7-8267-7ee7-af9b-7b8bff488880" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019c4eb7-8267-791c-973a-0be7719c3929" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019c4eb7-8267-7ee7-af9b-7b8bff488880" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019c4eb7-8267-791c-973a-0be7719c3929" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019c4eb7-8267-7d1c-ab91-ce4f12b6e934" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019c4eb7-8267-791c-973a-0be7719c3929" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019c4eb7-8267-7d1c-ab91-ce4f12b6e934" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c4eb7-8267-7d1c-ab91-ce4f12b6e934_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c4eb7-8267-7d1c-ab91-ce4f12b6e934" xlink:to="loc_us-gaap_EquityComponentDomain_019c4eb7-8267-7d1c-ab91-ce4f12b6e934_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c4eb7-8267-7f03-8eba-d3cf92813518" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c4eb7-8267-7d1c-ab91-ce4f12b6e934" xlink:to="loc_us-gaap_EquityComponentDomain_019c4eb7-8267-7f03-8eba-d3cf92813518" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c4eb7-8267-763b-9ffa-bc46c0372095" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c4eb7-8267-7f03-8eba-d3cf92813518" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c4eb7-8267-763b-9ffa-bc46c0372095" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_019c4eb7-8267-7c2d-8b97-29717005c334" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c4eb7-8267-763b-9ffa-bc46c0372095" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_019c4eb7-8267-7c2d-8b97-29717005c334" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019c4eb7-8267-79e3-a469-cd93f171f7fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c4eb7-8267-763b-9ffa-bc46c0372095" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019c4eb7-8267-79e3-a469-cd93f171f7fa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019c4eb7-8267-7cde-9119-1ae0c1af94ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c4eb7-8267-763b-9ffa-bc46c0372095" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019c4eb7-8267-7cde-9119-1ae0c1af94ee" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c4eb7-8267-7c54-ba15-3df572aab3e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019c4eb7-8267-7ee7-af9b-7b8bff488880" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c4eb7-8267-7c54-ba15-3df572aab3e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019c4eb7-8267-727b-a92a-e46d2a824e2b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c4eb7-8267-7c54-ba15-3df572aab3e7" xlink:to="loc_us-gaap_StockholdersEquity_019c4eb7-8267-727b-a92a-e46d2a824e2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent_019c4eb7-8267-7974-8965-ceab495bc882" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c4eb7-8267-7c54-ba15-3df572aab3e7" xlink:to="loc_us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent_019c4eb7-8267-7974-8965-ceab495bc882" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_019c4eb7-8267-7862-826d-9f212e9b7835" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c4eb7-8267-7c54-ba15-3df572aab3e7" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_019c4eb7-8267-7862-826d-9f212e9b7835" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019c4eb7-8267-724f-a8ce-50df8e6e9a81" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_019c4eb7-8267-730c-b436-257dcaabaf73" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAociCurrentPeriodTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019c4eb7-8267-7ee7-af9b-7b8bff488880" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_019c4eb7-8267-730c-b436-257dcaabaf73" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.aosmith.com/role/SubsequentEventDetails" xlink:type="simple" xlink:href="aos-20260331.xsd#SubsequentEventDetails"/>
  <link:definitionLink xlink:role="http://www.aosmith.com/role/SubsequentEventDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_019c4eb7-8267-7ee5-98e5-f304a65483dc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_019c4eb7-8267-7ee4-96f2-a30c7c526d30" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_019c4eb7-8267-7ee5-98e5-f304a65483dc" xlink:to="loc_us-gaap_SubsequentEventTable_019c4eb7-8267-7ee4-96f2-a30c7c526d30" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019dda23-d34a-7ffd-8005-473de9eda0e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019c4eb7-8267-7ee4-96f2-a30c7c526d30" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019dda23-d34a-7ffd-8005-473de9eda0e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019dda23-d34a-7ffd-8005-473de9eda0e7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019dda23-d34a-7ffd-8005-473de9eda0e7" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019dda23-d34a-7ffd-8005-473de9eda0e7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019dda23-d34a-7b85-bc71-dc9c826f031e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019dda23-d34a-7ffd-8005-473de9eda0e7" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019dda23-d34a-7b85-bc71-dc9c826f031e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019dda23-fa2d-7b05-8dcb-2128f77435ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019dda23-d34a-7b85-bc71-dc9c826f031e" xlink:to="loc_us-gaap_SubsequentEventMember_019dda23-fa2d-7b05-8dcb-2128f77435ff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_019dda24-174d-7f07-ba67-00f24df85004" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019c4eb7-8267-7ee4-96f2-a30c7c526d30" xlink:to="loc_srt_StatementScenarioAxis_019dda24-174d-7f07-ba67-00f24df85004" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019dda24-174d-7f07-ba67-00f24df85004_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_019dda24-174d-7f07-ba67-00f24df85004" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019dda24-174d-7f07-ba67-00f24df85004_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019dda24-174d-7ede-89c8-86c085a3f29e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_019dda24-174d-7f07-ba67-00f24df85004" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019dda24-174d-7ede-89c8-86c085a3f29e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_019dda24-30b5-7b7d-8d9f-32438326ef21" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_019dda24-174d-7ede-89c8-86c085a3f29e" xlink:to="loc_srt_ScenarioForecastMember_019dda24-30b5-7b7d-8d9f-32438326ef21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCharges_019dda23-4f27-72d6-a1d4-3a91df18ced7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestructuringCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019c4eb7-8267-7ee5-98e5-f304a65483dc" xlink:to="loc_us-gaap_RestructuringCharges_019dda23-4f27-72d6-a1d4-3a91df18ced7" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
