Patrick Cantlay punched a 17-foot putt to beat Bryson DeChambeau and win the BMW Championship in a six-hole playoff at Caves Valley Golf Club in Baltimore.
Cantlay secured his place in the playoffs with a 21-foot putt for birdie on the 18th.
The title is the 29-year-old American's third at this year's PGA Tour and enters next week's Tour Championship in first place in the FedEx Cup.
Rory McIlroy, who shot a 67, was fourth behind by five shots.
Cantlay, the new world number four, has also secured one of six automatic seats on the US Ryder Cup squad.
He joins Dustin Johnson, Collin Morikawa, Brooks Koepka, Justin Thomas, and DeChambeau in Steve Stricker's squad for the 43rd Ryder Cup at Whistling Straits next month.
An exciting last-round battle between Cantlay and DeChambeau produced a birdie feast as they both shot 66s to finish on 27-under-par.
DeChambeau, who had narrowly missed a round of 59 two days earlier, missed four putts to win the tournament.
After a ding-dong shootout separated the two players from the pack of pursuers, DeChambeau led by one with a hole remaining.
However, Cantlay - who has been putting on beautifully all week - punctured from 21 feet and DeChambeau's birdie effort slipped past to send the two players into extra time.
With DeChambeau even on the first extra hole, Cantlay nearly pocketed for a birdie from the rough of the greenside and then sank his return putt to extend the playoff, with DeChambeau failing with putts to win on the second and third holes. extra.
In the fourth, DeChambeau managed to make a brave par despite he found water with his push to force a fifth, which both players observed.
Returning back to hole 18, both players hit the green in twos and Cantlay's 17-foot birdie putt proved enough to secure victory when DeChambeau missed his eight-foot attempt.
"I'm focused as much as possible on every single shot and try not to let my mind go beyond the moment I'm in," Cantlay said, after the win.
"So I let the chips fall where they do. I try not to get caught up in being out for 45 yards or whatever. I just try to lock myself in and do my best at that moment, and my best is good enough. "