FNB CORP/PA/

UNITED STATES

SECURITIES

AND

EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐

Check the appropriate box:

F.N.B. Corporation

(Name of Registrant as Specified in its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Letter from our Chairman, President and Chief Executive Officer

Dear Shareholder:

We will hold our Annual Meeting of Shareholders at 8:30 AM, Eastern Time, on Wednesday, May 6, 2026. This year’s Annual Meeting of Shareholders will be held in an interactive, virtual-only format through a live webcast that will be available atwww.virtualshareholdermeeting.com/FNB2026. We believe the virtual meeting format conveniently enables our shareholders, regardless of geographic location, to participate and engage in the meeting. The virtual Annual Meeting presentation will be available online during the meeting and, during the 30 days following the meeting, a replay of the meeting will be posted on F.N.B. Corporation’s website atwww.fnb-online.com/investors. For further information about how to participate in the virtual meeting, please see Accessing Our Annual Meeting which is located immediately before the Proxy Statement Table of Contents.

Agendas

At our Annual Meeting, our shareholders will act on the following matters: (i) election of 10 director nominees named in the accompanying Proxy Statement to our Board of Directors; (ii) adoption of an advisory resolution to approve the 2025 compensation of our named executive officers; (iii) ratification of the appointment of Ernst & Young LLP as our independent registered public accounting firm for 2026; and (iv) any other matter that is properly presented at our Annual Meeting in compliance with our bylaws.

Your Vote Is Important

Your vote is important regardless of how many shares of F.N.B. Corporation stock you own. If you hold stock in more than one account or name, you will receive a proxy card for each.

Whether or not you plan to log in to our Annual Meeting, please complete, sign, date and promptly return the enclosed proxy card in the postage-paid envelope we have provided to permit your shares to be represented at our Annual Meeting. Alternatively, you may vote by the Internet, by our QR Code feature or by telephone simply by following the instructions on your proxy card. By voting now, your vote will be counted even if you are unable to log in to our Annual Meeting.

Please indicate on the card whether you plan to log in to our Annual Meeting. If you participate and wish to vote at our virtual Annual Meeting, you may withdraw your proxy at that time.

I would be remiss if I did not mention our Independent Lead Director, William B. Campbell, who will be retiring from our Board effective as of the date of our Annual Meeting, and extend my great appreciation for his distinguished service, dedication, leadership, and mentorship to many, including myself. He instilled in all of us a desire to put the shareholders first, and his presence on the Board will be missed. Best wishes to Director Campbell in his future endeavors. As always, our directors, management and employees thank you for your continued interest in and support of F.N.B. Corporation. Vincent J. Delie, Jr. Chairman, President and Chief Executive Officer

Notice of 2026 Annual Meeting of Shareholders

Date and Time: May 6, 2026 | 8:30 A.M. Eastern Time

Virtual-Only Meeting: www.virtualshareholdermeeting.com/FNB2026

Items of Business: FNB encourages you to vote “FOR” the following proposals: 1. To elect the 10 nominees named in this Proxy Statement to serve on our Board of Directors until the 2027 Annual Meeting. (Page 5) 2. To adopt an advisory resolution for approval of the 2025 compensation of our named executive officers as disclosed in this Proxy Statement. (Page 36) 3. To ratify the appointment of Ernst & Young LLP as our independent public accounting firm for 2026. (Page 88)

Meeting Details

See Accessing Our Annual Meeting beginning on the next page and other useful information in About Our Annual Meeting in Annex A.

Record Date

Only shareholders of record at the close of business on March 9, 2026, are entitled to receive notice of, and to vote at, the Annual Meeting.

Proxy Voting

Make your vote count. Please vote your shares promptly to allow the presence of a quorum during the Annual Meeting. Voting prior to the Annual Meeting will not prevent you from voting your shares during the Annual Meeting, as your proxy vote is revocable at your option. See below for how you can vote your shares:

BY ORDER OF THE BOARD OF

DIRECTORS,

James G. Orie

Chief Legal Officer and Corporate Secretary

OUR NOTICE OF ANNUAL MEETING, 2026 PROXY STATEMENT, 2025 ANNUAL REPORT AND 2025 FORM 10-K ARE AVAILABLE AT

http://materials.proxy.vote.com/302520