LOUISVILLE, Kentucky - A new era in golf has been well and truly established as world No.1 Rory McIlroy claimed his fourth major, the second in succession, in a riveting PGA Championship.
McIlroy earned his second Wanamaker trophy less than a month after winning the British Open and just a week removed from claiming the World Golf Championship Bridgestone Invitational with a three-under-par 68 final round good enough for a one-shot win.
A final hole par in near darkness left the Northern Irishman at 16-under-par for the tournament, edging five-time major winner Phil Mickelson who fired a 66 to finish at 15-under-par.
Sweden's Henrik Stenson (66) and American Rickie Fowler (68) shared third at 14-under.
Jason Day (72) and Adam Scott (69) were the best-placed Australians at nine-under par, a distant seven shots back in a tie for 15th.
Day was just one shot off the lead early in the final round but was left to rue an awful day on the greens.
In a brilliant final round where five players held the lead, McIlroy, Mickelson, Stenson and Fowler each had a chance to win over the final three holes but the world No.1 held firm.
As the overnight leader McIlroy made the turn and was quickly three back when Fowler birdied the 10th ahead of him.
But McIlroy bulleted a three wood to the par-five green in two to just seven feet and buried the eagle putt to pull within one.
By the 13th hole he had drawn level at the top and as the other three challengers made a costly bogey down the stretch he was alone in the lead with three holes to play.
A stunning approach from a fairway bunker on the 17th led to a critical birdie and a two-shot lead and while Mickelson birdied the last ahead of him, par was enough for McIlroy to win.
At 25 years, 3 months and 6 days old he becomes the fourth-youngest player to win four majors behind Tom Morris Jr, Tiger Woods and Jack Nicklaus.
He is the first back-to-back major winner since Padraig Harrington won the same double in 2008.