UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

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*** Exercise Your Right to Vote *** Important Notice Regarding the Availability of Proxy Materials for the Annual Meeting of Stockholders to Be Held on April 27, 2021. D34462-P51252-Z79306 UNITED STATES STEEL CORPORATION UNITED STATES STEEL CORPORATION 600 GRANT STREET SUITE 1500 PITTSBURGH, PA 15219 Meeting Information Meeting Type: Annual Meeting For holders as of: March 1, 2021 Date: April 27, 2021 Time: 8:00 AM Location: Meeting live via the Internet-please visit www.virtualshareholdermeeting.com/X2021. The company will be hosting the meeting live via the Internet this year. To attend the meeting via the Internet please visit www.virtualshareholdermeeting.com/X2021 and be sure to have the information that is printed in the box marked by the arrow XXXX XXXX XXXX XXXX (located on the following page). You are receiving this communication because you hold shares in the company named above. This is not a ballot. You cannot use this notice to vote these shares. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. You may view the proxy materials online at www.proxyvote.com, scan the QR Barcode on the reverse side, or easily request a paper copy (see reverse side). We encourage you to access and review all of the important information contained in the proxy materials before voting. See the reverse side of this notice to obtain proxy materials and voting instructions.

Before You Vote How to Access the Proxy Materials Proxy Materials Available to VIEW or RECEIVE: NOTICE AND PROXY STATEMENTANNUAL REPORT How to View Online: Have the information that is printed in the box marked by the arrowXXXX XXXX XXXX XXXX (located on the following page) and visit: www.proxyvote.com, or scan the QR Barcode below. How to Request and Receive a PAPER or E-MAIL Copy: If you want to receive a paper or e-mail copy of these documents, you must request one. There is NO charge for requesting a copy. Please choose one of the following methods to make your request: BY INTERNET:www.proxyvote.com 2) BY TELEPHONE: 1-800-579-1639 3) BY E-MAIL*:sendmaterial@proxyvote.com * If requesting materials by e-mail, please send a blank e-mail with the information that is printed in the box marked by the arrow XXXX XXXX XXXX XXXX (located on the following page) in the subject line. Requests, instructions and other inquiries sent to this e-mail address will NOT be forwarded to your investment advisor. Please make the request as instructed above on or before April 14, 2021 to facilitate timely delivery. VIEW MATERIALS & VOTE How To Vote Please Choose One of the Following Voting Methods SCAN TO Vote at the Meeting: You may attend the meeting virtually and you may vote during the meeting at www.virtualshareholdermeeting.com/X2021. Vote By Internet: Go to www.proxyvote.com or from a smartphone, scan the QR Barcode above. Have the information that is printed in the box marked by the arrow page) available and follow the instructions. XXXX XXXX XXXX XXXX (located on the following D34463-P51252-Z79306

Voting Items THE BOARD OF DIRECTORS RECOMMENDS A VOTE FOR EACH OF THE NOMINEES IN PROPOSAL 1 AND FOR PROPOSALS 2, 3 AND 4. Proposal 1. Election of Directors 1a. Tracy A. Atkinson 1b. David B. Burritt 1c. John J. Engel Proposal 3. RatificationofappointmentofPricewaterhouseCoopers LLP as independent registered public accounting firm Proposal 4. Approval of the Amended and Restated 2016 Omnibus Incentive Compensation Plan 1d. John V. Faraci NOTE: Such other business as may properly come before the meeting or any adjournment thereof. 1e. Murry S. Gerber 1f. Jeh C. Johnson 1g. Paul A. Mascarenas 1h. Michael H. McGarry 1i. Eugene B. Sperling D34464-P51252-Z79306

D34465-P51252-Z79306