Shane Lowry carded a four-under-par 66 to win the WGC-Bridgestone Invitational by two strokes on Sunday.
Overnight leaders Justin Rose and Jim Furyk both fired two-over-par 72s to finish in a tie for third, while world number three Bubba Watson finished second after hitting a final-round 66.
Reigning Masters and U.S. Open champion Jordan Spieth ended in a tie for 10th after recording a final-round 66.
Lowry, who began the day two shots off the pace in third, enjoyed a bogey-free round that included two birdies on both the front and the back nine.
It was a birdie at the 10th following an approach shot that landed just two feet from the cup that proved the key, as it moved him two shots clear of the rest of the field with the finish line in sight. The Irishman proceeded to end his round with an 11-foot birdie putt at the 18th to finish on 11-under for the tournament.
Rose, who finished on seven-under-par, paid the price for a number of missed par putts on Sunday, including a five-footer at the seventh and a three-footer at the 10th. Furyk too struggled with his putter when he was called on to save par, and will have been disappointed with a four-foot miss at the fifth.
Watson started with a birdie at the second before handing that shot right back at the third with the first of two bogeys. Consecutive birdies at the eighth and ninth saw him take the turn in 33 and move to seven-under.
Another birdie followed at the 10th before he sunk a 27-foot birdie putt at the 13th. Just as Watson looked to be on track for a strong finish, he was pegged back by a bogey at the 15th after a missed six-foot par putt. The 36-year-old atoned for his mistake with a birdie at the 17th, but it wasn't quite enough to catch Lowry.
Spieth, who started the final round in a tie for 17th, surged up the leaderboard after making four birdies and a bogey on the front nine. His birdie at the fifth provided the highlight of his round when he sunk a 25-foot shot from the front center green-side bunker.
The world number two had a much quieter back nine, making two birdies and another bogey to finish on four-under-par and in a tie for 10th with Rickie Fowler, who carded a three-under-par 67.