McIlroy led by six shots going into the final round and never let anyone closer than two shots. He closed with a 1-under 71 for a two-shot victory over Sergio Garcia and Rickie Fowler.
Garcia put up the biggest fight. He was two shots behind when he left a shot in the pot bunker right of the 15th green and made bogey. Birdies on two of the last three holes were not enough to catch McIlroy.
McIlroy won the 2011 U.S. Open and the 2012 PGA Championship. He joins Jack Nicklaus and Tiger Woods as the only players with three different majors at age 25 or younger.