Glatfelter Corp

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 (Amendment No.)

Filed by the Registrantx

Filed by a Party other than the Registranto

Check the appropriate box:

Glatfelter Corporation

(Name of Registrant as Specified In Its Charter)

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

NOTICE OF ANNUAL MEETING OF SHAREHOLDERS

The 2024 Annual Meeting of Shareholders (the “Annual Meeting”) of Glatfelter Corporation (“Glatfelter,” the “Company,” “we,” “us,” or “our”), a Pennsylvania corporation, will be held on Friday, May 10, 2024 at 8:00 a.m. Eastern Time, to consider and act on the following proposals:

1. the election of seven members of the Board of Directors of the Company (the “Board”) to serve until our 2025 Annual Meeting of Shareholders and until their successors are elected and qualified;

2. the ratification of the appointment of Deloitte & Touche LLP as the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2024;

3. the advisory approval of the Company’s 2023 named executive officer compensation (“Say-on-Pay” vote); and

4. such other business as may properly come before the Annual Meeting.

Only holders of record of the Company’s common stock at the close of business on March 14, 2024 (the “Record Date”) will be entitled to notice of, and to vote at, the Annual Meeting.

If you are a holder of record of the Company’s common stock on the Record Date, it is important that your shares be represented and we encourage you to vote your shares in advance of the Annual Meeting. Please vote your shares by telephone at 1-800-690-6903, online atwww.proxyvote.com, or by completing and signing the enclosed proxy card and returning it promptly in the enclosed envelope (requiring no postage if mailed in the United States). If you choose, you may still vote online during the Annual Meeting, even if you previously voted by telephone, internet, or mail.

In order to encourage participation and minimize any logistical obstacles for our shareholders, we are holding the Annual Meeting exclusively in a virtual only format via live webcast on the internet, also known as a “virtual meeting.” There will not be a physical location for the Annual Meeting, and you will not be able to attend the Annual Meeting in person.

To participate in the Annual Meeting, you must log ontowww.virtualshareholdermeeting.com/GLT2024 (the “Meeting Website”) and enter the 16-digit control number found on your proxy card, voting instruction form, or Notice of Availability. Therefore, it is very important that you retain your proxy card, voting instruction form, or Notice of Availability if you wish to virtually attend the Annual Meeting. You may vote your shares and ask questions during the Annual Meeting by following the instructions available on the Meeting Website. We encourage you to access the Meeting Website prior to the start time to familiarize yourself with the virtual meeting platform and ensure you can hear the streaming audio. Online access will be available starting at 7:45 a.m. on May 10, 2024. Whether or not you plan to virtually attend the Annual Meeting, we urge you to vote and submit your proxy in advance of the Annual Meeting by one of the methods described above.

Jill L. Urey, Secretary

March 26, 2024

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE COMPANY’S 2024 ANNUAL MEETING OF SHAREHOLDERS TO BE HELD ON MAY 10, 2024: Glatfelter Corporation’s proxy statement for the 2024 Annual Meeting of Shareholders and 2023 Annual Report are available via the Internet at www.glatfelter.com/investors/financials-and-filings/.

2024 PROXY STATEMENT ›

2024 PROXY STATEMENT ›