Koepka, who was named the PGA Tour's player of the year earlier this month, carded an eight-under-par 64 on Sunday to finish on 21 under, four shots clear of fellow American Gary Woodland.

The 28-year-old will replace his Ryder Cup team-mate Dustin Johnson at the top of the rankings on Monday.

"To be world number one is something I dreamed of as a kid," Koepka said.

"I don't think this one's going to sink in yet.

"Everything I've done this year has been working, so I don't want to change anything - just keep improving.

"I'm so excited right now, you have no idea. I can't wait to go play again."

Three-time major champion Koepka, who won the US Open and US PGA Championship earlier this year, is the third player in 2018 to reach number one for the first time, after England's Justin Rose and fellow American Justin Thomas.

His final round in South Korea included chipping in for a birdie from the greenside rough at the par-four 16th.

Koepka's victory follows the Ryder Cup where he was left "heartbroken" that one of his tee shots resulted in a spectator losing the sight in her right eye.

He also denied reports he had a fight with team-mate Johnson after the event, which Europe won, although captain Jim Furyk later said they had a brief altercation.