Three-time major winner Brooks Koepka closed out victory in the CJ Cup at Jeju Island in South Korea to become world number one for the first time.

The four-shot success over compatriot Gary Woodland, who charged up from five strokes behind to briefly share the lead at the turn, was the American's third of the year - the others being the US Open and USPGA.

He will displace Ryder Cup team-mate Dustin Johnson, who did not play this week, when the rankings are officially confirmed on Monday.

"To be world number one is something I dreamed of as a kid and I don't think this one's going to sink in yet," he told his post-round press conference.

"Everything I've done this year it's 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."

Graeme McDowell finished in a tie for 41st. 

Koepka began the day with a three-shot lead but by the time he had reached the turn one-under for his round with three birdies and two bogeys he had been joined at the top by Woodland.


His fellow American had six birdies in seven holes on the front nine and four birdies in his next seven holes kept pace with Koepka but he bogeyed the par-three 17th and even though he gained that shot back at the last for a nine-under round of 63 his 17-under total did not look enough to keep his rival at bay.

So it proved as Koepka chipped in from 70-feet for birdie at the 16th and holed a 25ft eagle putt at the last to card a round of 64 for a 21-under total.

"I'm not somebody who's going to panic if things go the wrong way," added Koepka of his slow start.

"I felt like the one (birdie) at 15 was quite big with Gary making a charge."

Ryan Palmer also made a late charge as he birdied his last seven holes to shoot a course-record 62 and finish in a tie for third place with Rafa Cabrera Bello four shots off the lead.