OAKMONT, Pa. -- J.J. Spaun survived a terrible start and challenging elements to pull away from the pack and capture his first major championship with a two-stroke victory in the 125th U.S. Open at Oakmont Country Club on Sunday.

After birdieing the 17th hole to take a one-stroke lead, Spaun made a 64½-foot birdie putt on the 18th to secure his unlikely victory and defeat Scotland's Robert MacIntyre by two.

After Spaun's long putt fell in the cup, he dropped his putter, raised his arms and gave the crowd a fist pump. He hugged caddie Mark Carens and later embraced his wife, Melody, and two young daughters.

Spaun said he didn't look at the scoreboard as he walked up the 18th fairway because he didn't want to know if he had a two-stroke lead.

"I knew, based [on] what the crowd was saying, that I felt like if I two-putted, I would probably win," Spaun said. "But I didn't want to look because I didn't want to play defensive. I didn't want to do anything dumb, trying to protect a three-putt or something.

"About 8 feet out, I kind of went up to the high side to see if it had a chance of going in, and it was like going right in. I was just in shock, disbelief that it went in and it was over."

Spaun was the only golfer to finish under par at 1-under 279. He posted a 2-over 72 on Sunday and went 3 under on the back nine. Spaun will collect $4.3 million for the biggest payday of his career.

MacIntyre, who was attempting to become the first left-handed golfer to win the U.S. Open, finished 1-over 281.

Norway's Viktor Hovland finished third at 2-over 282.

Spaun grabbed the outright lead at even par by reaching the green with a 309-yard drive on the short par-4 17th hole. His eagle try from 18 feet slid past the hole, but he made a 3½-foot birdie putt to lead by one stroke.

On the 18th hole, Spaun drove his tee shot down the right side of the fairway. As he prepared to hit his second shot, rain began to fall on the soaked course. Spaun hit his approach to 64½ feet, setting up the dramatic finish.

England's Tyrrell Hatton was talking to reporters when Spaun made his winning putt.

"He's holed it," Hatton said. "Unbelievable. What a putt to win. That's incredible."

When Hatton was asked what Spaun was probably feeling, he said, "In shock, I would guess. Unbelievable. Fair play."

Spaun started the day only one stroke behind 54-hole leader Sam Burns but trailed by as many as four after carding bogeys on five of his first six holes.

Spaun, 34, is the first U.S. Open winner to start his final round with three consecutive holes over par, according to Elias Sports Bureau. He is only the fifth champion to finish birdie-birdie on his final two holes.

"It felt like, as bad as things were going, I just still tried to just commit to every shot," Spaun said. "I tried to just continue to dig deep. I've been doing it my whole life."

Spaun said the weather delay helped him reset after such a bad start. Josh Gregory, one of his coaches, told him on the range that he was "trying too hard."

"That's what I was doing," Spaun said. "I felt like I had a chance, a really good chance, to win the U.S. Open at the start of the day. It just unraveled very fast. But that break was actually the key for me to winning this tournament."

It was the biggest moment of Spaun's career. The Los Angeles native's only prior PGA Tour victory came in the 2022 Valero Texas Open. Ranked 25th in the Official World Golf Ranking, Spaun has played some of the best golf of his career this year. He was a two-time runner-up this season, losing to Rory McIlroy in a playoff at the Players Championship.

It was a wild finish to a final round at Oakmont Country Club that included a 96-minute weather delay and steady rain that made one of the most demanding golf courses in the world even more difficult.

"Look, it just wasn't easy out there," said Australia's Adam Scott, who posted a 9-over 79 and tied for 12th at 6 over. "All things being equal, it's Sunday of the U.S. Open, one of the hardest setups, and the conditions were the hardest of the week. Thank God it wasn't like this all week."

Six golfers had at least a share of the lead in the final round, and at one point, five were tied for first.

MacIntyre had a chance to get to even par but left a 33-foot birdie try on No. 18 a couple of feet short and settled for a 2-under 68 in the final round.

While MacIntyre was signing his scorecard, Hatton, one of four golfers tied at 1 over, chunked two shots out of a greenside bunker and made a bogey on No. 17 to fall one behind.

Burns, the 54-hole leader who looked in control on the front nine, fell two strokes back when he made a double bogey on No. 15, his second in five holes.

Scott, who was attempting to win his first major since the 2013 Masters, fell out of the tie for first when he carded back-to-back bogeys on Nos. 14 and 15.

After Spaun's forgettable start, he made five straight pars and then made a 40½-foot putt for birdie on the par-5 12th to move into a five-way tie for first at 1 over.

A 22-foot birdie on the par-4 14th gave Spaun the outright lead at even par, one stroke in front of Mexico's Carlos Ortiz, Hatton, Scott and Burns.

"That was unbelievable," Hovland said. "After his start, it just looked like he was out of it immediately. Everyone came back to the pack. I wasn't expecting that, really. I thought I had to shoot maybe 3-under par today to have a good chance, but obviously the conditions got really, really tough, and this golf course is just a beast."

Burns seemed in control heading to the back nine. He was the only golfer below par at 2 under and had a two-stroke lead over Scott after making the turn at 3-over 38 and picking up a birdie with a 10½-foot putt on the par-4 10th.

Then, Burns caught two unfortunate breaks on the 11th. His drive landed in a muddy divot in the first cut, altering his second shot. His ball ended up in the thick rough on an upslope above a fairway bunker. Burns needed three more shots to get on the green, resulting in a double-bogey 6 that dropped him to even par.

Burns followed that miscue with a bogey on the 12th, which dropped him into a five-way tie for first.

Burns finished in a tie for seventh at 4 over, along with world No. 1 Scottie Scheffler and Jon Rahm.