<?xml version="1.0" encoding="UTF-8"?>
<edgarSubmission xmlns="http://www.sec.gov/edgar/thirteenffiler" xmlns:com="http://www.sec.gov/edgar/common">
  <schemaVersion>X0202</schemaVersion>
  <headerData>
    <submissionType>13F-HR</submissionType>
    <filerInfo>
      <liveTestFlag>LIVE</liveTestFlag>
      <flags>
        <confirmingCopyFlag>false</confirmingCopyFlag>
        <returnCopyFlag>true</returnCopyFlag>
        <overrideInternetFlag>false</overrideInternetFlag>
      </flags>
      <filer>
        <credentials>
          <cik>0000937394</cik>
          <ccc>XXXXXXXX</ccc>
        </credentials>
      </filer>
      <periodOfReport>09-30-2025</periodOfReport>
    </filerInfo>
  </headerData>
  <formData>
    <coverPage>
      <reportCalendarOrQuarter>09-30-2025</reportCalendarOrQuarter>
      <filingManager>
        <name>HEARTLAND ADVISORS INC</name>
        <address>
          <com:street1>790 N WATER STREET</com:street1>
          <com:street2>SUITE 1200</com:street2>
          <com:city>MILWAUKEE</com:city>
          <com:stateOrCountry>WI</com:stateOrCountry>
          <com:zipCode>53202</com:zipCode>
        </address>
      </filingManager>
      <reportType>13F HOLDINGS REPORT</reportType>
      <form13FFileNumber>028-04131</form13FFileNumber>
      <crdNumber>000002943</crdNumber>
      <secFileNumber>801-19074</secFileNumber>
      <provideInfoForInstruction5>Y</provideInfoForInstruction5>
      <additionalInformation>Heartland Advisors, Inc. is a wholly-owned subsidiary of Heartland Holdings, Inc. and is therefore deemed to have shared-defined investment discretion for purposes of the reporting requirements under Section 13(f) of the Securities Exchange Act of 1934, as amended.</additionalInformation>
    </coverPage>
    <signatureBlock>
      <name>Vinita K. Paul</name>
      <title>Vice President, General Counsel &amp; Secretary</title>
      <phone>414-347-7777</phone>
      <signature>/s/ Vinita K. Paul</signature>
      <city>Milwaukee</city>
      <stateOrCountry>WI</stateOrCountry>
      <signatureDate>11-07-2025</signatureDate>
    </signatureBlock>
    <summaryPage>
      <otherIncludedManagersCount>0</otherIncludedManagersCount>
      <tableEntryTotal>237</tableEntryTotal>
      <tableValueTotal>1892907827</tableValueTotal>
      <isConfidentialOmitted>false</isConfidentialOmitted>
    </summaryPage>
  </formData>
</edgarSubmission>
