Koepka closed with a three-under-par 67 to convert a one-stroke third-round lead into a two-shot victory over fellow American and World No.2 Scottie Scheffler (65) and Norwegian Viktor Hovland (69) at Oak Hill Country Club in Rochester, New York.

By joining Jack Nicklaus and Tiger Woods in having his name etched on the Wanamaker Trophy at least three times since it became strokeplay in 1958, Koepka also atoned for his self-confessed Masters "choke" and became the first LIV Golf player to win a major since last year's formation of the Saudi-backed league.

The American finished with a nine-under-271 total just two years removed from career-threatening knee surgery.

"This is incredible. This is wild," Koepka said.

"I look back at where we were two years ago, everything that has gone on. I'm just so happy right now. I'm kind of at a loss for words.

"This is just the coolest thing."

Australian Cam Davis and American Kurt Kitayama equalled the low round of the championship with final-round 65s to share fourth at three-under with former U.S. Open champion Bryson DeChambeau (70) and secure coveted invitations to next year's Masters.

But the day belonged to 33-year-old Koepka.

Only three months ago, the former World No.1 aired his vulnerabilities during the Full Swing series on Netflix.

Koepka celebrates his fifth major on the 72nd green. PHOTO: Kevin C. Cox/Getty Images.

Koepka admitted to returning prematurely from career-threatening knee surgery in March 2021 as he struggled to regain the form and confidence propelling him to the 2017 and 2018 U.S. Open titles and back-to-back PGA Championships in 2018 and 2019.

But, finally fit and healthy again, he first signalled a resurgence with victory at the LIV Golf Invitational Jeddah last October.

Then he won LIV Golf Orlando last month before taking the lead heading into the final round at Augusta National.

He let a four-shot last-day lead slip with a defensive Sunday 75 to allow World No.1 Jon Rahm to steal the green jacket and vowed not to make the same mistake at Oak Hill.

Koepka was true to his word.

"I look back at where we were two years ago, everything that has gone on. I'm just so happy right now. I'm kind of at a loss for words. This is just the coolest thing." – Brooks Koepka.

After three days of mostly rain and cold, bright sunshine made for ideal scoring conditions, and Koepka was quick to take advantage at Oak Hill with three birdies in his first four holes.

He stumbled briefly with successive bogeys on the 6th and 7th holes to have his lead trimmed back to one.

But it was all over when Hovland left his second shot in the bunker and chalked up a double bogey on No.16, and Koepka made birdie to jump three clear again.

Koepka joins Seve Ballesteros, Byron Nelson and Australian Peter Thomson with five major championship titles.

RELATED: Inside Koepka's winning bag

Only 12 players have won more.

"I don't know the list of guys who have won five times but to be in those groups of names is absolutely incredible," Koepka said.

"I'll be honest, it's something I'm not even sure I dreamed of it as a kid, that I was going to win this many."