content: <?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
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      <submissionType>144</submissionType>
      <filerInfo>
        <filer>
          <filerCredentials>
            <cik>0001720314</cik>
            <ccc>XXXXXXXX</ccc>
          </filerCredentials>
        </filer>
        <liveTestFlag>LIVE</liveTestFlag>
  
  
  
      </filerInfo>
    </headerData>
    <formData>
      <issuerInfo>
        <issuerCik>0001701732</issuerCik>
        <issuerName>Altair Engineering, Inc.</issuerName>
        <secFileNumber>001-38263</secFileNumber>
        <issuerAddress>
          <com:street1>1820 E. Big Beaver Road</com:street1>
          <com:city>Troy</com:city>
          <com:stateOrCountry>MI</com:stateOrCountry>
          <com:zipCode>48083</com:zipCode>
        </issuerAddress>
        <issuerContactPhone>248-614-2400</issuerContactPhone>
        <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>James Ralph Scapa</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
        <relationshipsToIssuer>
          <relationshipToIssuer>Director</relationshipToIssuer>
          <relationshipToIssuer>Officer</relationshipToIssuer>
        </relationshipsToIssuer>
      </issuerInfo>
      <securitiesInformation>
        <securitiesClassTitle>Class A Common Stock</securitiesClassTitle>
        <brokerOrMarketmakerDetails>
          <name>J.P. Morgan Securities LLC</name>
          <address>
            <com:street1>390 Madison Avenue</com:street1>
            <com:street2>6th Floor</com:street2>
            <com:city>New York</com:city>
            <com:stateOrCountry>NY</com:stateOrCountry>
            <com:zipCode>10017</com:zipCode>
          </address>
        </brokerOrMarketmakerDetails>
        <noOfUnitsSold>39000</noOfUnitsSold>
        <aggregateMarketValue>3698370</aggregateMarketValue>
        <noOfUnitsOutstanding>59427617</noOfUnitsOutstanding>
        <approxSaleDate>09/30/2024</approxSaleDate>
        <securitiesExchangeName>NASDAQ</securitiesExchangeName>
      </securitiesInformation>
      <securitiesToBeSold>
        <securitiesClassTitle>Class A Common Stock</securitiesClassTitle>
        <acquiredDate>11/01/2017</acquiredDate>
        <natureOfAcquisitionTransaction>Direct Investment by the James R. Scapa Declaration of Trust dated 03/05/87</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>19500</amountOfSecuritiesAcquired>
        <paymentDate>11/01/2017</paymentDate>
        <natureOfPayment>N/A</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Class A Common Stock</securitiesClassTitle>
        <acquiredDate>11/01/2017</acquiredDate>
        <natureOfAcquisitionTransaction>Direct Investment by the JRS Investments LLC</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>19500</amountOfSecuritiesAcquired>
        <paymentDate>11/01/2017</paymentDate>
        <natureOfPayment>N/A</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>James Scapa Declaration of Trust Dated 03/05/87</name>
          <address>
            <com:street1>C/o Altair Engineering, Inc.</com:street1>
            <com:street2>1820 East Big Beaver Road</com:street2>
            <com:city>Troy</com:city>
            <com:stateOrCountry>MI</com:stateOrCountry>
            <com:zipCode>48083</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Class A Common Stock</securitiesClassTitle>
        <saleDate>07/29/2024</saleDate>
        <amountOfSecuritiesSold>6500</amountOfSecuritiesSold>
        <grossProceeds>572707</grossProceeds>
      </securitiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>James Scapa Declaration of Trust Dated 03/05/87</name>
          <address>
            <com:street1>C/o Altair Engineering, Inc.</com:street1>
            <com:street2>1820 East Big Beaver Road</com:street2>
            <com:city>Troy</com:city>
            <com:stateOrCountry>MI</com:stateOrCountry>
            <com:zipCode>48083</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Class A Common Stock</securitiesClassTitle>
        <saleDate>08/28/2024</saleDate>
        <amountOfSecuritiesSold>6500</amountOfSecuritiesSold>
        <grossProceeds>578739</grossProceeds>
      </securitiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>JRS Investments LLC</name>
          <address>
            <com:street1>C/o Altair Engineering, Inc.</com:street1>
            <com:street2>1820 East Big Beaver Road</com:street2>
            <com:city>Troy</com:city>
            <com:stateOrCountry>MI</com:stateOrCountry>
            <com:zipCode>48083</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Class A Common Stock</securitiesClassTitle>
        <saleDate>07/29/2024</saleDate>
        <amountOfSecuritiesSold>6500</amountOfSecuritiesSold>
        <grossProceeds>572707</grossProceeds>
      </securitiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>JRS Investments LLC</name>
          <address>
            <com:street1>C/o Altair Engineering, Inc.</com:street1>
            <com:street2>1820 East Big Beaver Road</com:street2>
            <com:city>Troy</com:city>
            <com:stateOrCountry>MI</com:stateOrCountry>
            <com:zipCode>48083</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Class A Common Stock</securitiesClassTitle>
        <saleDate>08/28/2024</saleDate>
        <amountOfSecuritiesSold>6500</amountOfSecuritiesSold>
        <grossProceeds>578739</grossProceeds>
      </securitiesSoldInPast3Months>
      <remarks>Of the 39,000 shares being filed,  19,500 shares will be sold by the James R. Scapa Declaration of Trust dated 03/05/87, James R. Scapa as Trustee and 19,500 shares will be sold by the JRS Investments LLC, James R. Scapa as Manager</remarks>
      <noticeSignature>
        <noticeDate>09/30/2024</noticeDate>
        <planAdoptionDates>
          <planAdoptionDate>03/11/2024</planAdoptionDate>
        </planAdoptionDates>
        <signature>/s/ J.P. Morgan Securities LLC as agent and attorney-in-fact for James Ralph Scapa</signature>
      </noticeSignature>
    </formData>
  </edgarSubmission>
metadata_documents: [{"type": "144", "sequence": "1", "filename": "primary_doc.xml", "secsgml_size_bytes": 6654}]
text: 144
  0001720314
  XXXXXXXX
  LIVE
  0001701732
  Altair Engineering, Inc.
  001-38263
  1820 E. Big Beaver Road
  Troy
  MI
  48083
  248-614-2400
  James Ralph Scapa
  Director
  Officer
  Class A Common Stock
  J.P. Morgan Securities LLC
  390 Madison Avenue
  6th Floor
  New York
  NY
  10017
  39000
  3698370
  59427617
  09/30/2024
  NASDAQ
  Class A Common Stock
  11/01/2017
  Direct Investment by the James R. Scapa Declaration of Trust dated 03/05/87
  Issuer
  N
  19500
  11/01/2017
  N/A
  Class A Common Stock
  11/01/2017
  Direct Investment by the JRS Investments LLC
  Issuer
  N
  19500
  11/01/2017
  N/A
  N
  James Scapa Declaration of Trust Dated 03/05/87
  C/o Altair Engineering, Inc.
  1820 East Big Beaver Road
  Troy
  MI
  48083
  Class A Common Stock
  07/29/2024
  6500
  572707
  James Scapa Declaration of Trust Dated 03/05/87
  C/o Altair Engineering, Inc.
  1820 East Big Beaver Road
  Troy
  MI
  48083
  Class A Common Stock
  08/28/2024
  6500
  578739
  JRS Investments LLC
  C/o Altair Engineering, Inc.
  1820 East Big Beaver Road
  Troy
  MI
  48083
  Class A Common Stock
  07/29/2024
  6500
  572707
  JRS Investments LLC
  C/o Altair Engineering, Inc.
  1820 East Big Beaver Road
  Troy
  MI
  48083
  Class A Common Stock
  08/28/2024
  6500
  578739
  Of the 39,000 shares being filed,  19,500 shares will be sold by the James R. Scapa Declaration of Trust dated 03/05/87, James R. Scapa as Trustee and 19,500 shares will be sold by the JRS Investments LLC, James R. Scapa as Manager
  09/30/2024
  03/11/2024
  /s/ J.P. Morgan Securities LLC as agent and attorney-in-fact for James Ralph Scapa