Vijay Singh beat Chris DiMarco and Justin Leonard in a three-hole play-off to take the year's final major.
US unless stated
-8 Vijay Singh (Fij)*, Justin Leonard, Chris DiMarco
-7 Ernie Els (SA), Chris Riley
-6 Phil Mickelson, KJ Choi (Kor), Paul McGinley (Irl)
-5 Robert Allenby (Aus), Ben Crane, Adam Scott (Aus), Stephen Ames (Can)
* wins in play-off
The trio tied at eight under par after a dramatic fourth round at Whistling Straits on Sunday.
But the 41-year-old Fijian birdied the first hole of the play-off, the 10th, to take a lead he never relinquished.
When DiMarco and Leonard failed to birdie the last, the world number three was left with a simple tap-in for par and his third major title.
Singh's serene play in the three-way shoot-out was in marked contrast to what had gone before. In fact, his birdie at the opening play-off hole was his first of the day.
His four-over-par 76, which included a double bogey at the fourth, will go down as the worst winning round at a major since Reg Whitcombe's at the 1938 Open.
And Singh would not have been allowed to shine in the play-off if playing partner Leonard had closed out a two-shot advantage with three to play.
But the 1997 Open champion bogeyed the 16th and 18th to take the contest to extra holes with Singh and the 35-year-old DiMarco, who had earlier seen his birdie putt at the last stop agonisingly short of the hole.
DiMarco's consolation is that his one-under 71 to reach the play-off was enough to earn him a place in Hal Sutton's US Ryder Cup team.
The 32-year-old Leonard would have joined him there by right if he had held on at Whistling Straits. Now he must wait to see if Sutton will give him a wild card.
Singh, who won this event in 1998 and the Masters in 2000, was magnanimous in victory.
"Justin was so unlucky and it is sad to see somebody win it the way I did," he said.
"I didn't think I played badly, but my putter fell asleep on me. I played really well in the play-off, though.
"I just hung in there. I said I am going to make a shot sooner or later. It looked ugly when you look at the score because it was four over. But it was a good four over for me.
"This is the biggest accomplishment in my career. This makes my year."
One shot behind the leading trio were Ernie Els and Chris Riley on seven under.
For Riley there was also the prize of a Ryder Cup berth, but Els will be left wondering what might have been.
The 34-year-old South African reached 10 under par as early as the 10th on Friday but was unable to maintain his form over the weekend.
A final round of 73 was symptomatic of a season that has seen him win three times on tour but fail to convert winning positions in all four majors.
And a bogey at the last robbed Els of the second place finish he needed to oust Tiger Woods as world number one.
With Masters champion Phil Mickelson tied for sixth on six under with KJ Choi and Ireland's Paul McGinley - another to do wonders for his Ryder Cup hopes - the status quo at the top of the rankings remains the same.
Woods, who finished way down the field on two under, is still officially the world's best, but Singh and Els are closer than anybody has been for five years and it is now only a matter of time before one of them passes their great rival.
Of what promised to be a strong European challenge at the lakeside links on Sunday, only McGinley can take any satisfaction. Darren Clarke, Brian Davis, Luke Donald and Padraig Harrington all fell away to finish outside the top 10.