X0304 4 2012-01-12 0 0001137789 Seagate Technology plc STX 0001388390 MOSLEY WILLIAM D SEAGATE TECHNOLOGY PLC 10200 S. DE ANZA BOULEVARD CUPERTINO CA 95014 0 1 0 0 EVP, Sales and Marketing Ordinary Shares 2012-01-12 4 M 0 17500 13.73 A 31790.5977 D Ordinary Shares 2012-01-12 4 M 0 29166 4.045 A 60956.5977 D Ordinary Shares 2012-01-12 4 S 0 26666 19.00 D 34290.5977 D Ordinary Shares 2012-01-12 4 S 0 20000 19.00 D 14290.5977 D Ordinary Shares 2012-01-13 4 M 0 20000 4.045 A 34290.5977 D Ordinary Shares 2012-01-13 4 S 0 20000 19.50 D 14290.5977 D NQ Stock Options 13.73 2012-01-12 4 M 0 17500 0.00 D 2009-09-12 2015-09-12 Ordinary Shares 17500 11667 D NQ Stock Options 4.045 2012-01-12 4 M 0 29166 0.00 D 2010-01-30 2016-01-30 Ordinary Shares 29166 510834 D NQ Stock Options 4.045 2012-01-13 4 M 0 20000 0.00 D 2010-01-30 2016-01-30 Ordinary 20000 490834 D Shares were sold under a 10b5-1 trading plan adopted by the Reporting Person on May 24, 2011. Shares were sold under a 10b5-1 trading plan adopted by the Reporting Person on February 22, 2011. 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 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. /S/ Roberta S Cohen for William D Mosley 2012-01-13