<SEC-DOCUMENT>0000860413-25-000063-index.html : 20250516
<SEC-HEADER>0000860413-25-000063.hdr.sgml : 20250516
<ACCEPTANCE-DATETIME>20250516163209
ACCESSION NUMBER:		0000860413-25-000063
CONFORMED SUBMISSION TYPE:	DEFA14A
PUBLIC DOCUMENT COUNT:		3
FILED AS OF DATE:		20250516
DATE AS OF CHANGE:		20250516

FILER:

	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:		DEFA14A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-34653
		FILM NUMBER:		25959824

	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
</SEC-HEADER>
<DOCUMENT>
<TYPE>DEFA14A
<SEQUENCE>1
<FILENAME>a2024defa14aproxysupplement.htm
<DESCRIPTION>DEFA14A
<TEXT>
Document 1 - file: a2024defa14aproxysupplement.htm

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

</DOCUMENT>
<DOCUMENT>
<TYPE>GRAPHIC
<SEQUENCE>3
<FILENAME>image1.jpg
<DESCRIPTION>GRAPHIC
<TEXT>
Document 3 - file: image1.jpg

</DOCUMENT>
</SEC-DOCUMENT>