<SEC-DOCUMENT>0001967940-25-000063.txt : 20250902
<SEC-HEADER>0001967940-25-000063.hdr.sgml : 20250902
<ACCEPTANCE-DATETIME>20250902165241
ACCESSION NUMBER:		0001967940-25-000063
CONFORMED SUBMISSION TYPE:	144
PUBLIC DOCUMENT COUNT:		1
FILED AS OF DATE:		20250902
DATE AS OF CHANGE:		20250902

SUBJECT COMPANY:	

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			FIRST INTERSTATE BANCSYSTEM INC
		CENTRAL INDEX KEY:			0000860413
		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
		ORGANIZATION NAME:           	02 Finance
		EIN:				810331430
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		144
		SEC ACT:		1933 Act
		SEC FILE NUMBER:	001-34653
		FILM NUMBER:		251286303

	BUSINESS ADDRESS:	
		STREET 1:		401 NO 31ST STREET
		CITY:			BILLINGS
		STATE:			MT
		ZIP:			59101
		BUSINESS PHONE:		4062555311

	MAIL ADDRESS:	
		STREET 1:		401 NO 31ST STREET
		CITY:			BILLINGS
		STATE:			MT
		ZIP:			59101

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	FIRST INTERSTATE BANCSYSTEM OF MONTANA INC
		DATE OF NAME CHANGE:	19930615

REPORTING-OWNER:	

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Susan Scott Heyneman Trust, Susan Heyneman & First Interstate Wealth Management Co-Trustees
		CENTRAL INDEX KEY:			0001908880
		ORGANIZATION NAME:           	
		EIN:				000000000
		STATE OF INCORPORATION:			MT
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		144

	BUSINESS ADDRESS:	
		STREET 1:		PO 30918
		CITY:			BILLINGS
		STATE:			MT
		ZIP:			59116
		BUSINESS PHONE:		406-255-5239

	MAIL ADDRESS:	
		STREET 1:		PO 30918
		CITY:			BILLINGS
		STATE:			MT
		ZIP:			59116
</SEC-HEADER>
<DOCUMENT>
<TYPE>144
<SEQUENCE>1
<FILENAME>primary_doc.xml
<TEXT>
<XML>
<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
  <headerData>
    <submissionType>144</submissionType>
    <filerInfo>
      <filer>
        <filerCredentials>
          <cik>0001908880</cik>
          <ccc>XXXXXXXX</ccc>
        </filerCredentials>
      </filer>
      <liveTestFlag>LIVE</liveTestFlag>


    </filerInfo>
  </headerData>
  <formData>
    <issuerInfo>
      <issuerCik>0000860413</issuerCik>
      <issuerName>FIRST INTERSTATE BANCSYSTEM INC</issuerName>
      <secFileNumber>001-34653</secFileNumber>
      <issuerAddress>
        <com:street1>401 NO 31ST STREET</com:street1>
        <com:city>BILLINGS</com:city>
        <com:stateOrCountry>MT</com:stateOrCountry>
        <com:zipCode>59101</com:zipCode>
      </issuerAddress>
      <issuerContactPhone>4062555311</issuerContactPhone>
      <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>Susan Scott Heyneman Trust, Susan Heyneman &amp; First Interstate Wealth Management Co-Trustees</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
      <relationshipsToIssuer>
        <relationshipToIssuer>10% Stockholder</relationshipToIssuer>
      </relationshipsToIssuer>
    </issuerInfo>
    <securitiesInformation>
      <securitiesClassTitle>Common Stock</securitiesClassTitle>
      <brokerOrMarketmakerDetails>
        <name>Piper Sandler &amp; Co Inc</name>
        <address>
          <com:street1>350 N 5th St Ste 1000</com:street1>
          <com:city>Minneapolis</com:city>
          <com:stateOrCountry>MN</com:stateOrCountry>
          <com:zipCode>55401</com:zipCode>
        </address>
      </brokerOrMarketmakerDetails>
      <noOfUnitsSold>40000</noOfUnitsSold>
      <aggregateMarketValue>1308800.00</aggregateMarketValue>
      <noOfUnitsOutstanding>104856752</noOfUnitsOutstanding>
      <approxSaleDate>09/02/2025</approxSaleDate>
      <securitiesExchangeName>Nasdaq</securitiesExchangeName>
    </securitiesInformation>
    <securitiesToBeSold>
      <securitiesClassTitle>Common Stock</securitiesClassTitle>
      <acquiredDate>01/02/1976</acquiredDate>
      <natureOfAcquisitionTransaction>Pre IPO Shares</natureOfAcquisitionTransaction>
      <nameOfPersonfromWhomAcquired>NA</nameOfPersonfromWhomAcquired>
      <isGiftTransaction>N</isGiftTransaction>
      <amountOfSecuritiesAcquired>40000</amountOfSecuritiesAcquired>
      <paymentDate>01/02/1976</paymentDate>
      <natureOfPayment>Cash</natureOfPayment>
    </securitiesToBeSold>
    <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Susan Scott Heyneman Trust C/O First Interstate Bank</name>
        <address>
          <com:street1>401 N 31ST ST FL 1</com:street1>
          <com:city>Billings</com:city>
          <com:stateOrCountry>MT</com:stateOrCountry>
          <com:zipCode>59101</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common Stock</securitiesClassTitle>
      <saleDate>07/14/2025</saleDate>
      <amountOfSecuritiesSold>55000</amountOfSecuritiesSold>
      <grossProceeds>1711231.50</grossProceeds>
    </securitiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Susan Scott Heyneman Trust C/O First Interstate Bank</name>
        <address>
          <com:street1>401 N 31ST ST FL 1</com:street1>
          <com:city>Billings</com:city>
          <com:stateOrCountry>MT</com:stateOrCountry>
          <com:zipCode>59101</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common Stock</securitiesClassTitle>
      <saleDate>08/01/2025</saleDate>
      <amountOfSecuritiesSold>55000</amountOfSecuritiesSold>
      <grossProceeds>1532052.50</grossProceeds>
    </securitiesSoldInPast3Months>
    <noticeSignature>
      <noticeDate>09/02/2025</noticeDate>
      <planAdoptionDates>
        <planAdoptionDate>06/12/2025</planAdoptionDate>
      </planAdoptionDates>
      <signature>Alex Johnson, a duly authorized representative of Piper Sandler &amp; Co Corporate &amp; Venture Services FA, as attorney-in-fact for Susan Scott Heyneman TR</signature>
    </noticeSignature>
  </formData>
</edgarSubmission>
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</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
