Diamondback Energy Inc. American Stock Prospectus (Version as of March 12, 2026)

Diamondback Energy, Inc.Common Stock This prospectus supplement relates to the resale of up to an aggregate of 11,000,000 shares of commonstock of Diamondback Energy, Inc., a Delaware corporation, by the stockholder named in this prospectussupplement (the “selling stockholder”). We are not selling any shares of our common stock under thisprospectus supplement and we will not receive any of the proceeds from the sale of shares by the selling The selling stockholder has granted the underwriters an option to purchase up to an aggregateadditional 1,650,000 shares of common stock, solely to cover over-allotments, at the public offering price,less the underwriting discounts and commissions, within 30days from the date of this prospectus References to “underwriters” in this prospectus supplement refer to the underwriters named in the“Underwriting” section of this prospectus supplement. The underwriters expect to deliver the shares against payment on or about March12, 2026. Book-Running ManagersCitigrou J.P. Morgan Evercore ISI TABLE OF CONTENTS ABOUT THIS PROSPECTUS SUPPLEMENT This prospectus supplement is part of a registration statement that was filed with the U.S. Securitiesand Exchange Commission (the “SEC”) using a “shelf” registration process and consists of two parts. Thefirst part is this prospectus supplement, which describes the specific terms of this offering and alsosupplements and updates information contained in the accompanying prospectus and the documentsincorporated by reference into this prospectus supplement and the accompanying prospectus. The secondpart is the accompanying prospectus, which provides more general information, some of which may notapply to this offering. This prospectus supplement may add, update, or change information contained in theaccompanying prospectus. Generally, when we refer to this prospectus, we are referring to both parts of thisdocument combined. In addition, in this prospectus, as permitted by law, we “incorporate by reference”information from other documents that we file with the SEC. This means that we can disclose important It is important for you to read and consider all information contained or incorporated by reference inthis prospectus supplement and the accompanying prospectus. You should read both this prospectussupplement and the accompanying prospectus, as well as the documents incorporated by reference into this Neither we, the selling stockholder nor the underwriters have authorized any other person to provideyou with information different from that contained in this prospectus supplement, the accompanying baseprospectus and any free writing prospectus prepared by or on behalf of us relating to this offering of You should not assume that the information appearing in this prospectus supplement, the accompanyingprospectus or any document incorporated by reference is accurate at any date other than as of the date ofeach such document. Our business, financial condition, results of operations and prospects may have The distribution of this prospectus supplement and accompanying prospectus may be restricted by lawin certain jurisdictions. You should inform yourself about and observe any of these restrictions. Thisprospectus supplement and accompanying prospectus do not constitute, and may not be used in connection When used in this prospectus supplement or in the accompanying prospectus, the terms“Diamondback,” the “Company,” “our,” “we,” or “us” refer to Diamondback Energy, Inc. and its CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS This prospectus supplement and the accompanying prospectus, including documents incorporated byreference herein and therein, may contain “forward-looking statements” within the meaning of Section27Aof the Securities Act of 1933, as amended (the “Securities Act”) and Section21E of the Securities ExchangeAct of 1934, as amended (the “Exchange Act”), which involve risks, uncertainties and assumptions. Allstatements, other than statements of historical fact, including statements regarding our: future performance;business strategy; future operations (including drilling plans and capital plans); estimates and projections ofrevenues, losses, costs, expenses, returns, cash flow, and financial position; reserve estimates and our abilityto replace or increase reserves; anticipated benefits or other effects of strategic transactions (including therecently completed Double Eagle Acquisition and Viper’s Sitio Acquisition (in each case, as defined below)and other acquisitions or divestitures); and plans and objectives of management (including plans for futurecash flow from operations and for executing environmental strategies) are forward-looking statements. Factors that could cause our outcomes to differ materially include (but are not limited to) the following: ••••••geopolitics and market conditions, including changes in supply and demand levels for oil, naturalgas, and natural gas liquids, and the resulting impact