GPGI, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION​

Washington, DC 20549

SCHEDULE 14A

(RULE 14a-101)

INFORMATION REQUIRED IN PROXY STATEMENT

SCHEDULE 14A INFORMATION

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Securities Exchange Act of 1934

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Preliminary Proxy Statement

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Definitive Proxy Statement

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Definitive Additional Materials

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Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11.

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PROXY STATEMENT

April 24, 2026

Dear Stockholder:

You are cordially invited to the annual meeting of stockholders (the “Annual Meeting”) of GPGI, Inc. (the “Company”), which will be held virtually at 10:00 a.m. Eastern Time on June 11, 2026. We have adopted a virtual format for our Annual Meeting to provide a consistent experience to all stockholders regardless of location. You will be able to attend the Annual Meeting and vote during the Annual Meeting via live webcast through the link www.virtualshareholdermeeting.com/GPGI2026.

In connection with the Annual Meeting, you will be asked to consider and vote on certain proposals that are more fully described in the accompanying proxy statement (the “Proxy Statement”). Whether or not you plan to attend the Annual Meeting, we urge you to read the Proxy Statement and consider such information carefully before voting.

THE BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT OUR STOCKHOLDERS

VOTE “FOR” PROPOSALS 1, 2 AND 4 AND “ONE YEAR” ON PROPOSAL 3 PRESENTED IN THE PROXY STATEMENT.

Your vote is very important. Even if you plan to attend the Annual Meeting, if you are a stockholder of record of Class A Common Stock, par value $0.0001 per share (the “Class A Common Stock”), please submit your proxy by Internet, mail or telephone as soon as possible to make sure that your shares are represented at the Annual Meeting, or you may submit your proxy at the Annual Meeting. If you hold your shares of Class A Common Stock in “street name” through a bank, broker or other nominee, you must vote in accordance with the voting instructions provided to you by such bank, broker or other nominee, which include instructions for voting by Internet or telephone.

On behalf of the Board of Directors, we thank you for your support of GPGI, Inc.

Yours sincerely,

This Proxy Statement is dated April 24, 2026. Holders of record of the Company’s Class A Common Stock at the close of business on April 15, 2026 are entitled to receive notice of, and to vote at, the Annual Meeting.

Instructions on how to vote your shares are contained on the “Important Notice Regarding the Availability of Proxy Materials,” which is expected to be mailed on or about April 24, 2026.

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

TO BE HELD ON JUNE 11, 2026

To the Stockholders of GPGI, Inc. (“we,” “our,” or the “Company”):

NOTICE IS HEREBY GIVEN that the 2026 annual meeting of stockholders of the Company (the “Annual Meeting”) will be held virtually at 10:00 a.m. Eastern Time on June 11, 2026.

Virtual Annual Meeting

In order to facilitate stockholder attendance and participation, after careful consideration, the Company’s Board of Directors (the “Board”) has determined to hold a virtual annual meeting in order to enable stockholders to participate from any location and at no cost to stockholders. We believe this is the right choice for the Company at this time, as it enables engagement with our stockholders, regardless of size, resources, or physical location. We are committed to ensuring that stockholders will be afforded substantially the same rights and opportunities to participate as they would at an in-person meeting. You will be able to attend the Annual Meeting online and vote your shares electronically during the Annual Meeting by visiting www.virtualshareholdermeeting.com/GPGI2026.

To participate in the virtual Annual Meeting, you will need the 16-digit control number included on your “Important Notice Regarding the Availability of Proxy Materials,” proxy card, or voting instruction form. The Annual Meeting webcast will begin promptly at 10:00 a.m. Eastern Time. We encourage you to access the Annual Meeting prior to the start time and you should allow ample time for the check-in procedures. We will have technicians ready to assist you with any technical difficulties you may have accessing the virtual Annual Meeting. A phone number where you can obtain technical assistance will be available on the Annual Meeting website on the day of the Annual Meeting.

Items of Business

At the Annual Meeting, you will be asked to consider and vote upon the following proposals:

A proposal to elect four Class II directors to serve on the Company’s Board of Directors for a term expiring at the 2029 annual meeting of stockholders and until their successors are duly elected and qualified, or until such director’s earlier resignation, removal, or death;

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A proposal to approve, on an advisory basis, the 2025 compensation of our named executive officers as disclosed in the accompanying Proxy Statement;

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A proposal to approve, on an advisory basis, the frequency (i.e., every one, two or three years) of future advisory votes to approve the compensation of our named executive officers; and

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A proposal to ratify the appointment of Ernst & Young LLP as the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2026.

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The foregoing items of business are more fully described in the accompanying Proxy Statement, which you should read in its entirety and carefully consider prior to casting any votes in connection with such proposals. The Board has set the close of business on April 15, 2026, as the record date (the “Record Date”) for determining stockholders entitled to notice of, and to vote at, the Annual Meeting. Each outstanding share of the Company’s Class A Common Stock as of the Record Date entitles its holder to cast one vote on each matter to be voted upon. A list of the stockholders as of the Record Date will be available for inspection by stockholders, for any purpose germane to the Annual Meeting, at the Company’s offices during normal business hours for a period of 10 days prior to the Annual Meeting. The list will also be made available electronically for inspection by stockholders in attendance at the virtual Annual Meeting.

All stockholders are cordially invited to attend the Annual Meeting virtually. Regardless of whether you plan to attend the Annual Meeting, we hope you will vote as soon as possible. Instructions on how to vote your shares via the Internet are contained on the “Important Notice Regarding the Availability of Proxy Materials,” which is expected to be mailed on or about April 24, 2026. Instructions on how to obtain a paper copy of our Proxy Statement and annual report to stockholders for the fiscal year ended December 31, 2025, are listed on the “Important Notice Regarding the Availability of Proxy Materials.” These materials can also be viewed online by following the instructions listed on our proxy card. If you choose to receive a paper copy of our Proxy Statement and annual report, you may vote your shares by completing and returning the proxy card that will be enclosed.

IMPORTANT NOTICE ON THE AVAILABILITY OF PROXY MATERIALS

FOR THE ANNUAL MEETING TO BE HELD ON JUNE 11, 2026.

OUR PROXY STATEMENT AND ANNUAL REPORT FOR THE FISCAL YEAR ENDED

DECEMBER 31, 2025 ARE AVAILABLE AT WWW.PROXYVOTE.COM.

By Order of the Board of Directors

David A.P. Marshall

Chief Legal Counsel and Corporate Secretary

April 24, 2026

Somerset, New Jersey​