Sec Form 4 Filing - MOSLEY WILLIAM D @ Seagate Technology plc - 2012-01-12

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL OMB Number: 3235-0287 Expires: November 30, 2011 Estimated average burden hours per response... 0.5

1. Name and Address of Reporting Person MOSLEY WILLIAM D 2. Issuer Name and Ticker or Trading Symbol Seagate Technology plc [ STX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) EVP, Sales and Marketing (Last) (First) (Middle) SEAGATE TECHNOLOGY PLC, 10200 S. DE ANZA BOULEVARD 3. Date of Earliest Transaction (MM/DD/YY) 01/12/2012 (Street) CUPERTINO, CA95014 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Ordinary Shares 01/12/2012 M 17,500 A $ 13.73 31,790.5977 D Ordinary Shares 01/12/2012 M 29,166 A $ 4.045 60,956.5977 D Ordinary Shares 01/12/2012 S 26,666 D $ 19 ( 1 ) 34,290.5977 D Ordinary Shares 01/12/2012 S 20,000 D $ 19 ( 2 ) 14,290.5977 D Ordinary Shares 01/13/2012 M 20,000 A $ 4.045 34,290.5977 D Ordinary Shares 01/13/2012 S 20,000 D $ 19.5 ( 2 ) 14,290.5977 D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares NQ Stock Options $ 13.73 01/12/2012 M 17,500 09/12/2009( 3 ) 09/12/2015 Ordinary Shares 17,500 $ 0 11,667 D NQ Stock Options $ 4.045 01/12/2012 M 29,166 01/30/2010( 4 ) 01/30/2016 Ordinary Shares 29,166 $ 0 510,834 D NQ Stock Options $ 4.045 01/13/2012 M 20,000 01/30/2010( 3 ) 01/30/2016 Ordinary 20,000 $ 0 490,834 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other MOSLEY WILLIAM D SEAGATE TECHNOLOGY PLC 10200 S. DE ANZA BOULEVARD CUPERTINO, CA95014 EVP, Sales and Marketing Signatures /S/ Roberta S Cohen for William D Mosley 01/13/2012 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Shares were sold under a 10b5-1 trading plan adopted by the Reporting Person on May 24, 2011. ( 2 )Shares were sold under a 10b5-1 trading plan adopted by the Reporting Person on February 22, 2011. ( 3 )Options granted the Reporting Person under the Issuer's 2004 Stock Compensation Plan are subject to a four-year vesting schedule. One quarter of the option shares vested on January 30, 2010. The remaining shares are vesting and will continue to vest proportionally each month over the 36 months following January 30, 2010 ( 4 )Options Granted to the Reporting Person under the Issuer's 2004 Stock Compensation Plan are subject to a four-year vesting schedule. One quarter of the option shares vested on September 12, 2009. The remaining shares are vesting and will continue to vest proportionally each month over the 36 months following September 12, 2009.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.