    <SEC-DOCUMENT>0000860413-21-000144-index.html : 20210414
    <SEC-HEADER>0000860413-21-000144.hdr.sgml : 20210414
    <ACCEPTANCE-DATETIME>20210414123638
    ACCESSION NUMBER:		0000860413-21-000144
    CONFORMED SUBMISSION TYPE:	DEFA14A
    PUBLIC DOCUMENT COUNT:		2
    FILED AS OF DATE:		20210414
    DATE AS OF CHANGE:		20210414

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			FIRST INTERSTATE BANCSYSTEM INC
    		CENTRAL INDEX KEY:			0000860413
    		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
    		IRS NUMBER:				810331430
    		STATE OF INCORPORATION:			MT
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		DEFA14A
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	001-34653
    		FILM NUMBER:		21825113

    	BUSINESS ADDRESS:
    		STREET 1:		P O BOX 30918
    		STREET 2:		401 NO 31ST STREET
    		CITY:			BILLINGS
    		STATE:			MT
    		ZIP:			59116-0918
    		BUSINESS PHONE:		4062555300

    	MAIL ADDRESS:
    		STREET 1:		P O BOX 30918
    		STREET 2:		401 NO 31ST STREET
    		CITY:			BILLINGS
    		STATE:			MT
    		ZIP:			59116-0918

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	FIRST INTERSTATE BANCSYSTEM OF MONTANA INC
    		DATE OF NAME CHANGE:	19930615
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>DEFA14A
    <SEQUENCE>1
    <FILENAME>defa14aproxysoliciting.htm
    <DESCRIPTION>DEFA14A
    <TEXT>
    Document 1 - file: defa14aproxysoliciting.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>2
    <FILENAME>noticeinternetavailability.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 2 - file: noticeinternetavailability.jpg

    </DOCUMENT>
    </SEC-DOCUMENT>