TROON, Scotland -- Xander Schauffele's critics used to say he didn't have the nerves or backbone to win one of golf's major championships.

Now, the 30-year-old PGA Tour star from San Diego can't stop winning them.

Two months after Schauffele captured his first major championship victory at the PGA Championship at Valhalla Golf Club in Louisville, Kentucky, he added a second one Sunday at the 152nd Open Championship at Royal Troon Golf Club.

"There's calmness and super stressful moments when you're trying to win a major championship," Schauffele said. "I felt them in the past -- the ones I didn't win -- and I let them get to me. Today, I felt like I did a pretty good job of weathering the storm when I needed to."

On a day when seven golfers started the final round within one shot of leader Billy Horschel, Schauffele was the man holding the Claret Jug at the iconic links course on Scotland's west coast. He posted a 6-under 65 on Sunday, just like he did in the final round of the PGA Championship, and his 72-hole total of 9-under 275 put him two strokes ahead of Horschel and England's Justin Rose.

South Africa's Thriston Lawrence was another stroke back.

"It was hard," Schauffele said. "It was very difficult. I think winning the first one helped me a lot today on the back nine. I had some feeling of calmness come through. It was very helpful on what has been one of the hardest back nines I've ever played in a tournament.

"I mean, it's a dream come true to win two majors in one year. It took me forever just to win one, and to have two now is something else."

Schauffele described Sunday's bogey-free round as the "best round I've played."

According to ESPN Stats & Information, Schauffele is the first golfer in the Masters era (since 1934) to have multiple final rounds of 65 or better in majors in the same year.

It's the seventh consecutive major won by an American golfer, the longest such streak since they captured 13 straight from 1974 to 1977.

It's the first year since 1982 that U.S. golfers claimed all four majors -- Scottie Scheffler won the Masters, and Bryson DeChambeau captured the U.S. Open.

Schauffele is the first golfer since Brooks Koepka in 2018 (U.S. Open and PGA Championship) to claim two majors in one season. It's only the seventh time a player has won the PGA Championship and The Open in the same year; Rory McIlroy was the last to do it, in 2014.

Schauffele's victory Sunday required patience. He opened his final round with five straight pars, and he fell behind Horschel, Lawrence and Rose. Schauffele kick-started his round with back-to-back birdies on Nos. 6 and 7 and made the turn at 2-under 34.

Although the difficult par-4 11th, known as The Railway, ended plenty of golfers' hopes this week, Schauffele avoided trouble off the tee and hit his approach from 171 yards to 2 feet for another birdie to get to 6 under. He moved into a tie for first when Lawrence made a bogey on the 12th.

Schauffele then seized control with another pair of birdies, making a 16-foot uphill putt on the par-4 13th and a 12-footer on the par-3 14th. He moved to 8 under and had a two-stroke lead with four holes to play.

Schauffele added another birdie on the par-5 16th to stretch his lead to three shots.

He will head to next month's Olympics tournament outside Paris to defend his gold medal.

"He's obviously now learning that the winning is easy," Rose said of Schauffele. "He has a lot of horsepower, do you know what I mean? In the sense of he's good with a wedge, he's great with a putter, he hits the ball a long way, obviously his iron play is strong. So he's got a lot of weapons out there.

"I think probably one of his most unappreciated ones is his mentality. He's such a calm guy out there. I don't know what he's feeling, but he certainly makes it look very easy. He plays with a freedom, which kind of tells you as a competitor that he's probably not feeling a ton of the bad stuff. He's got a lot of runway ahead and a lot of exciting stuff ahead, I'm sure."

Even after waiting so long to win a major, Schauffele admits he can't help but think about the career Grand Slam after moving a step closer. He only needs to win the Masters and U.S. Open now to do it.

"I mean, before I had any majors, it's something I've always wanted," Schauffele said. "I'm one step closer and still have a long way to go. But if you don't see yourself doing it, you're never going to do it."

Several other golfers, including Scheffler, the No. 1-ranked player in the world, faltered down the stretch. Scheffler was looking for his seventh victory and second major championship title this season. He moved into the mix with back-to-back birdies on Nos. 7 and 8.

Scheffler's chances of winning a Claret Jug ended on the par-4 ninth, though. His approach shot was 15 yards short of the green. He putted to 6 feet and somehow three-putted from there, missing from 2 feet, 8 inches on the second attempt. Scheffler carded a double-bogey 6, dropping him to 2 under, four shots behind the leaders as he made the turn.

Scheffler also had a double bogey on the 18th. He posted a 1-over 72 and tied for seventh at 1-under 283.

Spain's Jon Rahm made one of the biggest moves after starting the day six shots behind Horschel. The two-time major champion made four birdies in his first seven holes to get to 2 under.

On the par-4 11th hole, Rahm pushed his tee shot toward the railway on the right. He hit a provisional tee shot but ended up finding his ball in a gorse bush. After a one-stroke penalty for an unplayable lie, Rahm made a bogey 5, dropping him to 1 under. He posted a 3-under 68 and finished at 1-under 283.

England's Daniel Brown, who grew up on a pig and cow farm and nearly gave up golf four years ago, carded four bogeys in his first six holes to fall back to even, five strokes behind the early leaders.

It was the end of one of the more remarkable stories in recent Open history. Brown made the field by draining a 20-foot putt in final qualifying. After missing the cut in six of his previous eight starts on the DP World Tour, he started the day only one shot behind Horschel. Brown was attempting to become only the fourth golfer since 1900 to win a major championship in his debut.

Brown was 3-over 74 in the final 18 holes, finishing at even-par 284, which tied him for 10th.

"Poor front nine, that's basically it," Brown said. "I struggled on the front nine, really. I don't think I scored as well as the guys around me on the front nine. The right-to-left wind, I couldn't really get to grips with that, but then felt a lot more comfortable when the wind was off the left on the back nine. A little bit to work on with a strong right-to-left breeze."

Two-time major champion Justin Thomas, who started the final round four strokes behind Horschel, took himself out of the hunt when he hit a wild tee shot and had to re-tee on the opening hole, resulting in a triple-bogey 7. Thomas tied for 31st at 6 over after posting a 6-over 77 in the final round.

Scotland's Calum Scott, an All-Big 12 selection last season at Texas Tech, won the Silver Medal as the low amateur. He carded a 5-over 76 on Sunday to finish at 8-over 292.