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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019df0b8-06d6-7e6d-a011-0b80d53d2e29,g:a366df16-435c-4b3e-ad8a-f276c41a41d3-->
<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.muellerwaterproducts.com/role/CoverPageDocument" xlink:type="simple" xlink:href="mwa-20260505.xsd#CoverPageDocument"/>
  <link:definitionLink xlink:role="http://www.muellerwaterproducts.com/role/CoverPageDocument" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_019df0b8-06d6-7655-9024-407f9e22367a" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_DocumentInformationTable_019df0b8-06d6-7655-9024-407f9e22367a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationDocumentAxis_019df0b8-06d6-70fe-a41b-027e31931cf1" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentInformationDocumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_019df0b8-06d6-7655-9024-407f9e22367a" xlink:to="loc_dei_DocumentInformationDocumentAxis_019df0b8-06d6-70fe-a41b-027e31931cf1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentDomain_019df0b8-06d6-70fe-a41b-027e31931cf1_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_DocumentInformationDocumentAxis_019df0b8-06d6-70fe-a41b-027e31931cf1" xlink:to="loc_dei_DocumentDomain_019df0b8-06d6-70fe-a41b-027e31931cf1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentDomain_019df0b8-06d6-7bec-bfbf-777e3952c37b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_DocumentInformationDocumentAxis_019df0b8-06d6-70fe-a41b-027e31931cf1" xlink:to="loc_dei_DocumentDomain_019df0b8-06d6-7bec-bfbf-777e3952c37b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019df0b8-06d6-7559-ad28-789cfdf52ec8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_EntityCentralIndexKey_019df0b8-06d6-7559-ad28-789cfdf52ec8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019df0b8-06d6-751d-a80a-5c093e92f8e5" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_EntityEmergingGrowthCompany_019df0b8-06d6-751d-a80a-5c093e92f8e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019df0b8-06d6-75e0-8e2e-47015d169012" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_Security12bTitle_019df0b8-06d6-75e0-8e2e-47015d169012" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_019df0b8-06d6-7782-ab22-fab261350782" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_WrittenCommunications"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_WrittenCommunications_019df0b8-06d6-7782-ab22-fab261350782" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019df0b8-06d6-7db9-9fd9-91ea84d707b4" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019df0b8-06d6-7db9-9fd9-91ea84d707b4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019df0b8-06d6-75a9-8bae-65e9f2c7c4e3" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_EntityFileNumber_019df0b8-06d6-75a9-8bae-65e9f2c7c4e3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019df0b8-06d6-7e76-ad34-cbdaa3e3b7f4" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_EntityTaxIdentificationNumber_019df0b8-06d6-7e76-ad34-cbdaa3e3b7f4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019df0b8-06d6-763c-b769-252192975c6f" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_EntityAddressAddressLine1_019df0b8-06d6-763c-b769-252192975c6f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_019df0b8-06d6-768c-b7eb-12c396df63df" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_EntityAddressAddressLine2_019df0b8-06d6-768c-b7eb-12c396df63df" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019df0b8-06d6-7699-8158-23c7b603b97e" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_EntityAddressCityOrTown_019df0b8-06d6-7699-8158-23c7b603b97e" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019df0b8-06d6-7a12-b928-6c2d29f99468" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_EntityAddressStateOrProvince_019df0b8-06d6-7a12-b928-6c2d29f99468" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019df0b8-06d6-76f1-ba4a-7cf13fc28da3" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_EntityAddressPostalZipCode_019df0b8-06d6-76f1-ba4a-7cf13fc28da3" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019df0b8-06d6-7fac-aaa5-e14fefaadbbb" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_CityAreaCode_019df0b8-06d6-7fac-aaa5-e14fefaadbbb" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019df0b8-06d6-73fa-ae00-d7dd4ad7770b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_LocalPhoneNumber_019df0b8-06d6-73fa-ae00-d7dd4ad7770b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_019df0b8-06d6-787f-8f1b-afdd206b8d99" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_SolicitingMaterial"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_SolicitingMaterial_019df0b8-06d6-787f-8f1b-afdd206b8d99" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_019df0b8-06d6-7684-9024-e424fa4548ee" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_PreCommencementTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_PreCommencementTenderOffer_019df0b8-06d6-7684-9024-e424fa4548ee" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_019df0b8-06d6-7be8-93ca-9ae9c6f9dbc7" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_PreCommencementIssuerTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_019df0b8-06d6-7be8-93ca-9ae9c6f9dbc7" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019df0b8-06d6-7605-a348-d4117709d0c2" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_TradingSymbol_019df0b8-06d6-7605-a348-d4117709d0c2" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019df0b8-06d6-7cd0-b454-5e98439f3116" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_SecurityExchangeName_019df0b8-06d6-7cd0-b454-5e98439f3116" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019df0b8-06d6-7730-97df-b183089513ce" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019df0b8-06d6-7b9a-baf3-71363ea98ac8" xlink:to="loc_dei_AmendmentFlag_019df0b8-06d6-7730-97df-b183089513ce" xlink:type="arc" order="19"/>
  </link:definitionLink>
</link:linkbase>
