FIRST INTERSTATE BANCSYSTEM INC

Overview

The Board is asking our stockholders to approve an amendment to our Charter to provide for a plurality

voting standard, the default voting standard for director elections under Delaware law, in the event of

a contested election of directors, to the extent set forth in our bylaws. The proposed amendment will

not change the currently in effect majority voting standard included in our Charter and bylaws for

uncontested director elections.

Providing for a plurality voting standard in a contested election would eliminate the risk of “holdover”

directors that could result from an election where neither the incumbent directors nor the

stockholder-nominated directors were to receive the requisite majority vote “for” election. Such a

holdover result could be deemed to frustrate the stockholders’ desire to replace the incumbent

directors up for reelection, who, following a contested election in which no director nominee were to

receive the requisite majority vote, would continue to serve as directors until their successors are duly

elected and qualified. The plurality voting standard is believed to be the prevailing best corporate

governance practice for contested director elections, as further discussed below.

Proposed Amendment

If this Proposal is approved by our stockholders, Article Seventh, Section (d), of our Charter will be

amended as follows (with the bold and underlined or stricken words showing the amended text):

(d)Directors Except as may otherwise be set forth in the Bylaws of the Corporation

with respect to plurality voting in the event of a contested election (as such term is

defined or used in the Bylaws) of directors, directors shall be elected by a majority of

the voting power of the shares of capital stock present in person or represented by proxy at an

annual meeting of shareholders and entitled to vote on the election of directors. There shall be

no cumulative voting for directors of the Corporation.

In furtherance of the foregoing, if this Proposal is approved by our stockholders and the Charter

amendment becomes effective, it currently is intended that Section 2.16(c) of our bylaws will read as

follows in relevant part applicable to contested elections and this proposed Charter amendment:

2.16 REQUIRED VOTE FOR DIRECTORS

(c) In the event of a contested election of directors, … directors shall be elected by a plurality

of the votes of the shares present in person or represented by proxy and voting for nominees in

the election of directors at any meeting for the election of directors at which a quorum is

present. For purposes of this Section 2.16, a contested election shall mean any election of

directors in which the number of candidates for election as directors at such meeting exceeds

the number of directors to be elected at such meeting as of the tenth (10th) day preceding the

date the Corporation first mails its notice of meeting for such meeting to the stockholders of

the Corporation.

Background and Reasons for the Proposed Amendment

As part of the Board’s ongoing corporate governance review process, our Board has evaluated our

corporate governance practices in light of evolving expectations of investors and proxy advisory firms

and prevailing market practice. In connection with that review, the Board considered the current

majority voting standard applicable to director elections under our governing documents, which is the

applicable standard even in contested elections of directors.

A governance structure that applies majority voting in director elections that are uncontested (where

the number of director nominees does not exceed the number of directors to be elected) and plurality

voting in director elections that are contested (where the number of director nominees exceeds the

number of directors to be elected) is widely viewed as a best corporate governance practice because it

promotes accountability while also ensuring that contested elections yield a clear result. In a

contested election, applying a majority voting standard (when the majority voting standard requires a

majority of the voting power of the shares of common stock present in person or represented by proxy

at an annual meeting of stockholders and entitled to vote on the election of directors to vote “for” a

candidate in order for the candidate to be elected) could create the possibility of a “failed election”—

failed because votes may be split among multiple candidates, or because abstentions and votes against

nominees, may prevent one or more of the nominees from receiving the required majority vote.

A failed election could result in uncertainty regarding election outcomes and could result in one or

more seats not being filled through the stockholder voting process at an annual meeting, including the

possibility that incumbent directors continue to serve as holdover directors until their successors are

duly elected and qualified, or that vacancies arise. By contrast, a plurality standard in a contested

election produces a definitive result because the nominees receiving the highest number of votes cast

“for” their election as a director are elected, which the Board believes more accurately reflects

stockholders’ preferences among competing nominees and is in the best interests of our stockholders.

Key Effects of the Proposed Amendment

If stockholders approve this Proposal and the Charter amendment becomes effective:

•Contested elections: plurality vote will be applicable to the extent set forth in our bylaws.

In the event of a “contested election” as discussed above under the caption “Proposal 2,

Proposed Amendment”, plurality voting, the default voting standard under Delaware law for

director elections under which the director nominees receiving the highest number of votes

“for” in the election of directors are elected, is intended to be applied.

•Uncontested elections: majority vote continues to be applicable as set forth in our Charter

and bylaws. In the event of an uncontested election, directors will continue to be elected by a

majority of the voting power of the shares present in person or represented by proxy and

entitled to vote on the election of directors. If an incumbent director does not receive the

required majority vote of stockholders “for” election in an uncontested election, under our

director resignation policy set forth in our bylaws, such director is required to promptly tender

his or her resignation for consideration of acceptance by the Board.

Our Board believes the foregoing voting standards applicable to director elections are the prevailing

best corporate governance practice for director elections.

If a quorum is present at the annual meeting, under Section 242 of the General Corporation Law of the

State of Delaware and our Charter and bylaws, approval of this Proposal requires the affirmative vote

of the holders of a majority of the outstanding shares of our common stock entitled to vote on the

Proposal. This means that the Charter amendment must receive the affirmative vote of more than 50%

of the total votes represented by all of our outstanding shares of common stock to be approved,

regardless of whether all of such shares are present and represented at the meeting. In addition,

because this Proposal constitutes a non‑routine matter, shares held in street name through brokers or

other nominees are not expected to be voted on this Proposal absent specific prior instruction from the

beneficial owners of such shares. As such, we are expecting there to be at least some so-called “broker

non-votes” on this Proposal. Because this vote requires a majority of the total outstanding shares of

our common stock entitled to vote on the Proposal, whether or not they are present at the meeting,

broker non-votes and abstentions will have the same effect as votes “AGAINST” this Proposal. If you

hold shares through a broker, bank or other nominee, please instruct your broker, bank or other

nominee how to vote your shares.

Effective Time; Filing of Amendment

If stockholders approve this Proposal, we intend to file the Certificate of Amendment to the Charter

with the Secretary of State of the State of Delaware as soon as practicable after the 2026 annual

meeting to give effect to the above-described amendment. The amendment is expected to become

effective upon filing (or such later effective time as may be specified in the filed amendment) with the

Secretary of State of the State of Delaware.

THE BOARD OF DIRECTORS RECOMMENDS THAT YOU VOTE “FOR” PROPOSAL 2.