The 33-year-old now has a hat-trick of PGA Championship titles, having held the lead going into the final round at the Oak Hill Country Club in New York.

American Koepka managed to hold off Norway's Viktor Hovland and compatriot Scottie Scheffler, who has been reinstated as the world number one, by two shots.

Koepka finished with a score of nine-under-par to clinch what is his first major since undergoing knee surgery.

"This is incredible," Koepka said, as he won the Wanamaker Trophy for a third time.

"I look back at where we were two years ago.

"I am just so happy right now; this is just the coolest thing.

"I don't know how many guys have won five times, but to be with those groups of names is absolutely incredible and I'll be honest I'm not even sure I dreamed of it as a kid.

"To win a major is always a big deal no matter where you're playing.

"All it does, I just think, is it validates it for myself.

"I guess maybe if anybody doubted it from Augusta [when he did not win The Masters after leading by two shots going into the final round] or whatever, any doubts anybody on TV might have or whatever, I'm back, I'm here.

"Pardon my language, but it's all the f***ing s*** I had to go through.

"No one knows.

"No one knows, I think, all the pain.

"There were a lot of times where I just couldn't even bend my knee.

"Yeah, it felt good. It felt really good."

Koepka joins Spain's Seve Ballesteros, Australian Peter Thomson, Byron Nelson of the United States, John Henry Taylor of England and Scotland's James Braid as a quintuple major winner.

Koepka endured persistent booing from fans during the tournament because of his controversial move to Saudi-backed tour LIV Golf.

The win sees him land a $3.15 million (£2.5 million/€2.9 million) cheque.