England’s Justin Rose won the WGC Champions title in Shanghai as world number one Dustin Johnson capitulated on the final day.
Johnson led by six shots and was eight clear of Rose after three rounds.
But Rose, 37, shot a five-under-par 67, which included eight birdies and three bogeys, to finish on 14 under.
American Johnson carded a five-over 77 to finish joint-second on 12 under, alongside Sweden’s Henrik Stenson and compatriot Brooks Koepka.
Johnson’s round included bogeys on the first, second, 12th, 15th and 16th at Sheshan Golf Club.
“It’s unbelievable,” said 2016 Olympic champion Rose.
“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.
“We all know the position DJ was in and today was the kind of day that the leader probably didn’t want. This is the kind of day where that kind of swing is possible.
“It was really tricky out there. I shot five under in tough conditions and he made a few mistakes.
“I played one of the best back nines I’ve played. To shoot 31 to come through, I saved my best till last.”
Rose and Stenson, the silver medallist at the Rio Olympics, were joint leaders with three holes to play.
But Rose shot two birdies and a par, while Stenson finished with a birdie, bogey and par.