Seagate Technology (STX) DEFA14A Additional proxy soliciting materials

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of

the Securities Exchange Act of 1934 (Amendment No.            )

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Seagate Technology public limited company

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*** Exercise Your Right to Vote *** Notice of Annual General Meeting of Shareholders and Important Notice Regarding the Availability of Proxy Materials for the Shareholder Meeting to Be Held on October 29, 2019. Meeting Information SEAGATE TECHNOLOGY PLC Meeting Type: Annual General Meeting For holders as of: September 3, 2019 Date: October 29, 2019 Time: 9:30 a.m., Local Time Location: InterContinental Hotel Simmonscourt Road Dublin 4, D04 A9K8 Ireland You are receiving this communication because you hold shares in the company named above. SEAGATE TECHNOLOGY PLC 38/39 FITZWILLIAM SQUARE This is not a ballot. You cannot use this notice to vote these DUBLIN 2, D02 NX53, IRELAND 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 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. P28197 proxy See the materials reverse and side voting of this instructions. notice to obtain E84023—

Before You Vote How to Access the Proxy Materials Proxy Materials Available to VIEW or RECEIVE: NOTICE AND PROXY STATEMENT FORM10-K How to View Online: Have the information that is printed in the box marked by the arrow XXXX XXXX XXXX XXXX (located on the following page) and visit: www.proxyvote.com. How to Request and Receive a PAPER orE-MAIL Copy: If you want to receive a paper ore-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: 1) BY INTERNET: www.proxyvote.com 2) BY TELEPHONE:1-800-579-16393) BYE-MAIL*: sendmaterial@proxyvote.com * If requesting materials bye-mail, please send a blanke-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 thise-mail address will NOT be forwarded to your investment advisor. Please make the request as instructed above on or before October 15, 2019 to facilitate timely delivery. How To Vote Please Choose One of the Following Voting Methods Vote In Person: If you wish to attend the meeting in person, you will need to bring your proof of identification along with either your Notice of Internet Availability of Proxy Materials or proof of stock ownership. At the meeting, you will need to request a ballot to vote these shares. If you are a shareholder who is entitled to attend the meeting and vote, but do not wish to attend the meeting in person, you are entitled to appoint a proxy or proxies to attend, speak and vote on your behalf. Such proxy is not required to be a shareholder of the Company. If you wish to appoint as proxy any person other than those specified on the Proxy Card, please contact Investor Relations at +1(408)658-1222 ore-mail stx@seagate.com. For directions to the meeting, P28197—please contact Investor Relations at +1(408)658-1222 ore-mail stx@seagate.com.Vote By Internet: To vote now by Internet, go to www.proxyvote.com. Have the information that is printed in the box E84024 marked by the arrow XXXX XXXX XXXX XXXX (located on the following page) available and follow the instructions.Vote By Mail: You can vote by mail by requesting a paper copy of the materials, which will include a Proxy Card.

Voting Items The Board of Directors (the “Board”) recommends you vote FOR each of the nominees listed in Proposal 1 and FOR Proposals 2, 3, 4, 5, 6 and 7. 1. Election of Directors 2. Approve, in an advisory,non-binding vote, the compensation of the Company’s named executive Nominees: officers(“Say-on-Pay”). 1a. William D. Mosley 3. Ratify, in anon-binding vote, the appointment of Ernst & Young LLP as the independent auditors of the Company, and authorize, in a binding vote, the Audit Committee of the Company’s Board of Directors to set the 1b. Stephen J. Luczo auditors’ remuneration.4. Approve our Amended and Restated 2012 Equity 1c. Mark W. Adams Incentive Plan.5. Grant the Board the authority to allot and issue shares. 1d. Judy Bruner 6. Grant the Board the authority toopt-out of statutorypre-emption rights. 1e. Michael R. Cannon 7. Determine the price range at which the Company can 1f. William T. Colemanre-allot shares that it acquires as treasury shares. 1g. Jay L. Geldmacher In their discretion, the proxies are authorized to vote on such other business as may properly come before the meeting and any adjournment or postponement of the meeting. 1h. Dylan Haggart 1i. Stephanie Tilenius 1j. Edward J. Zander—P28197 E84025

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