Justin Rose produced a brilliant finish to take advantage of a stunning collapse from world number one Dustin Johnson and win the WGC-HSBC Champions in Shanghai.
Rose began the final round eight shots behind Johnson and was still six adrift at the turn, but fired five birdies in a back nine of 31 to complete a closing 67, with Johnson slumping to a 77.
At 14 under par, Rose finished two shots ahead of Ryder Cup partner Henrik Stenson, Brooks Koepka and Johnson, who had started the day with a six-shot lead in pursuit of a record third World Golf Championship victory this year.
Rose's second WGC title lifts him from 13th in the world to sixth, with Koepka and Stenson now seventh and eighth respectively, pushing the absent Rory McIlroy down to ninth.
Paul Dunne finished with a disastrous seven-over 79 to tumble down the leaderboard and finish the tournament on one-over.
Of his increidble triumph, Rose said: "It's unbelievable.
"It's been a long time since I've won, or at least it feels like that. I've won every year since 2010, if you include the Olympics last year. I've left it late this year but it feels amazing.
"Obviously we all know the position DJ was in and I think today was the kind of day that the leader probably didn't want. You want a six-shot lead any time, but this is the kind of day where that kind of swing is possible.
"I shot five under in tough conditions and he had to play good golf to keep it around par today, and obviously he made a few mistakes. It was really tricky out there and obviously I played one of the best back nines I've played in forever.
"To shoot 31 on the back to come through, I saved my best till last."
Rose's 10th European Tour title lifts him to third in the Race to Dubai with three events remaining, albeit still more than a million points behind leader Tommy Fleetwood, who finished in a tie for 20th after a closing 74.
"It kind of gives me a realistic chance now, if I was to have a special end to the season with Turkey and Dubai," added Rose, who topped the money list in 2007.
Johnson, who won at Sheshan International in 2013, had recorded 22 birdies in the first three rounds but failed to manage a single one on Sunday.
The former US Open champion bogeyed the first two holes and dropped further shots on the 12th, 15th and 16th to join Greg Norman, Sergio Garcia and Spencer Levin as the only men since 1996 to lead a PGA Tour event by six shots with a round to play and fail to win.
"It was tough conditions today and I felt like I actually drove it pretty well, other than the drive on two," Johnson said.
"Even making the turn I'm two over, which is fine. I know I've got to just play solid on the back nine. I didn't make any putts. I felt like I rolled it good. Just nothing was going in the hole.
"I hit a couple of really bad iron shots. That was probably the key there on 14. I just chunked it. Same thing on 15, I just chunked it. That cost me two shots there.
"And then bogeying 16, that's just bad. So I just gave a few away."