Bryson DeChambeau capitalised on a late collapse from Rory McIlroy to win the US Open for a second time with a dramatic one-shot victory at Pinehurst No 2.
DeChambeau took a three-shot lead into the final day but found himself two behind when McIlroy - playing in the penultimate group - made four birdies in a five-hole stretch around the turn to boost his hopes of an elusive fifth major victory.
McIlroy remained one ahead until he followed back-to-back bogeys from the 15th with another at the par-four last, missing two putts from inside four feet over that closing stretch, as DeChambeau produced a sensational up and down at the last to secure his second major title.
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DeChambeau carded a final-round 71 to finish on six under and a shot clear of McIlroy, who remains without a major win since his 2014 PGA Championship success, with Tony Finau and Patrick Cantlay finishing a further shot back in third of Matthieu Pavon.
How DeChambeau edged McIlroy in major thriller
McIlroy - playing in the penultimate group alongside Cantlay - got off to the dream start when he rolled in from 20 feet at the first, then found himself within one of the lead after DeChambeau failed to save par from the back of the green at the fourth.
A terrible break for McIlroy at the par-five fifth saw his excellent approach run off a sloping green, with the Northern Irishman then chipping into a bunker from a poor lie on his way to a bogey that moved DeChambeau two clear.
McIlroy missed the green four times in five holes but continued to scramble for pars to stay in touch with DeChambeau, who produced an incredible up and down at the eighth and holed from 15 feet to remain on six under.
The lead was cut to one when McIlroy rolled in from 15 feet to birdie the ninth, with the 2011 US Open champion then draining a 25-footer at the par-five next to grab a share of the lead for the first time.
DeChambeau briefly edged back ahead when he also birdied the 10th and did well to save par at the next after finding a greenside bunker with his approach, only to see McIlroy pull back level with another long-range birdie at the 12th.
A two-shot swing saw McIlroy convert from five feet to pick up a shot at the driveable 13th, having taken a favourable bounce off a grandstand off the tee, as DeChambeau bogeyed the previous hole after an errant drive left him pitching out.
DeChambeau responded to make a two-putt birdie at the 13th to get within one on seven under, which was enough for a share of the lead when McIlroy missed the green off the 15th tee and carded a sixth bogey of the week on a par-three.
Nerves became clear from both players over the closing stretch, with DeChambeau three-putting from 25 feet at the 15th to fall one behind and then McIlroy inexplicably missing from two and a half feet to save par at the 16th.
McIlroy responded to get up and down from the sand at the 17th but gifted DeChambeau the lead at the last, where he failed to find the green in two and missed a putt to save par from inside four feet, falling him back to five under.
DeChambeau pulled his tee shot into the native area and missed the green with his second, only to produce a remarkable 55-yard pitch from the sand to four feet and convert the putt to complete a remarkable major Sunday.
"I felt like I was hitting the driver the way I wanted today," DeChambeau said in the trophy presentation. "I just kept staying the course focussed on trying as many fairways as I could even though I didn't but I got myself out of trouble really well but I can't believe that up and down, it was probably the best shot of my life.
"I was just trying to land it pretty much where I landed it. I knew that was huge to get up and down to win this huge prestigious championship. It's the highlight of my life."
What's next?
The PGA Tour season continues with the Travelers Championship, the latest of the Signature Events, with early coverage live on Thursday from 12.30pm via the red button and 5pm on Sky Sports Golf.
The final men's major of the year is The Open, taking place at Royal Troon from July 18-21, where DeChambeau will again be among the pre-tournament favourites. Stream the PGA Tour, majors and more with NOW.