Additional Proxy Soliciting Materials (Form DEFA14A)

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

DIAMONDBACK ENERGY, INC.

(Name of Registrant as Specified In Its Charter)

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

Online Go to www.envisionreports.com/FANG or scan the QR code - login details are located in the shaded bar below. Votes submitted electronically must be received by 1:00 A.M., Central Time, on May 20, 2026. Stockholder Meeting Notice 048NAC Important Notice Regarding the Availability of Proxy Materials for Diamondback Energy, Inc.'s Annual Meeting of Stockholders to be Held on May 20, 2026 Under the Securities and Exchange Commission rules, you are receiving this notice that the proxy materials for Diamondback Energy, Inc.'s Annual Meeting of Stockholders are available on the Internet. Follow the instructions below to view the proxy materials and vote online or to request a copy of the proxy materials. We encourage you to access and review the proxy materials before voting. The proxy materials consist of this Notice of the Annual Meeting, the Company's 2025 Annual Report to Stockholders, the Company's 2026 Proxy Statement and the Proxy Card. This communication is NOT a form for voting and presents only an overview of the more complete proxy materials, which contain important information and are available on the Internet, email or by mail. We encourage you to access and review the proxy materials before voting. www.envisionreports.com/FANG Easy Online Access - View your proxy materials and vote. Step 1: Go to www.envisionreports.com/FANG. Step 2: Click on Cast Your Vote or Request Materials. Step 3: Follow the instructions on the screen to log in. Step 4: Make your selections as instructed on each screen for your delivery preferences. Step 5: Vote your shares. When you go online, you can also help the environment by consenting to receive electronic delivery of future materials. Obtaining a Copy of the Proxy Materials - If you want to receive a paper or email copy of these documents, you must request one. There is no charge to you for requesting a copy. Please make your request for a copy as instructed on the reverse side on or before May 9, 2026 to facilitate timely delivery. 2 N O T 048NAC

Stockholder Meeting Notice Diamondback Energy, Inc.'s Annual Meeting of Stockholders will be held on May 20, 2026 at the Fasken Center, 500 West Texas Avenue, Midland, Texas 79701, at 10:00 A.M. Central Time. Proposals to be voted on at the meeting are listed below along with the Board of Directors' recommendations. The Board of Directors recommends a vote FOR all the nominees listed in Proposal 1, FOR Proposals 2 and 4 and 1 YEAR on Proposal 3: 1. Election of Directors: 01 - Vincent K. Brooks, 02 - Darin G. Holderness, 03 - Rebecca A. Klein, 04 - Stephanie K. Mains, 05 - Charles A. Meloy, 06 - Mark L. Plaumann, 07 - Robert K. Reeves, 08 - Lance W. Robertson, 09 - Travis D. Stice, 10 - Melanie M. Trent, 11 - Frank D. Tsuru, 12 - Kaes Van't Hof and 13 - Steven E. West 2. The approval, on an advisory basis, the compensation of the Company's named executive officers. 3. The approval, on an advisory basis, the frequency of holding an advisory vote on the compensation paid to the Company's named executive officers. 4. The ratification of the appointment of Grant Thornton LLP as the Company's independent auditor for the fiscal year ending December 31, 2026. PLEASE NOTE - YOU CANNOT VOTE BY RETURNING THIS NOTICE. To vote your shares you must go online or request a paper copy of the proxy materials to receive a proxy card. If you wish to attend and vote at the meeting, please bring this notice with you. Please check the proxy materials for directions to be able to attend the Annual Meeting and vote in person. Here's how to order a copy of the proxy materials and select delivery preferences: Current and future delivery requests can be submitted using the options below. If you request an email copy, you will receive an email with a link to the current meeting materials. PLEASE NOTE: You must use the number in the shaded bar on the reverse side when requesting a copy of the proxy materials. - Internet - Go to www.envisionreports.com/FANG. Click Cast Your Vote or Request Materials. - Phone - Call us free of charge at 1-866-641-4276. - Email - Send an email to [email protected] with "Proxy Materials Diamondback Energy, Inc." in the subject line. Include your full name and address, plus the number located in the shaded bar on the reverse side, and state that you want a paper or electronic copy of the meeting materials. To facilitate timely delivery, all requests for a paper copy of proxy materials must be received by May 9, 2026.