England's Justin Rose has become world number one for the first time after finishing in second place at the BMW Championship in Philadelphia.
The 38-year-old climbs from fourth and replaces Dustin Johnson after losing a play-off to American Keegan Bradley.
Rose, reigning Olympic champion and 2013 US Open winner, could have sealed victory with a par putt at the last regulation hole but missed narrowly.
"It's boyhood dream stuff, something I am incredibly proud of," Rose said.
"It's been a good stretch of golf. I've played solidly over the past year. I'm delighted to get to the top," he told Sky Sports.
On his putt at the last to win, he said: "I thought it was as good a putt as I've hit to win a tournament. To see it spin out was really unfortunate. I'd always envisaged getting to number one by winning tournaments.
"Last week's second was a good-feeling second and this one is a stinging-feeling second, but I know there is a bit of good news."
Rose, who last week finished two shots back as Bryson DeChambeau won the Dell Technologies Championship, is just the fourth Englishman to top the world rankings, after Sir Nick Faldo, Lee Westwood and Luke Donald.
He and Bradley finished on 20 under par after a rain-delayed final round and the 2011 US PGA champion required just one extra hole to seal victory.
Rose bogeyed the par-four 18th to hand the 32-year-old American his fourth PGA Tour win.
The final round had been scheduled for Sunday but was postponed until Monday after persistent rain made the Aronimink course unplayable.
Bradley began the day three shots behind Rose but moved up the leaderboard with a six-under-par 64 as Rose shot a 67.
Northern Ireland's Rory McIlroy, who trailed then-leader Rose by one shot after round three, finished fifth following a 68.
American 14-time major winner Tiger Woods closed with a 65, moving up to a share of sixth, one shot behind McIlroy.
England's Tommy Fleetwood only managed a 69 as he fell down the leaderboard to eighth from joint third.