Brooks Koepka is all smiles after sinking his putt on the 18th hole to win the CJ Cup on Sunday and become the new World No 1. Photo: Park Ji-ho/Yonhap via AP

JEJU, South Korea – Triple major champion Brooks Koepka will overtake Dustin Johnson and Justin Rose to become world number one for the first time after winning the CJ Cup on Sunday by four strokes.

Koepka shot a final round of eight-under-par 64 at the US PGA Tour event in South Korea, highlighted by a chip-in for birdie on the 16th, to finish 21-under-par.

The US PGA Tour Player of the Year Koepka captured first prize in the $9.5 million tournament with a four-round total of 267, four ahead of fellow American Gary Woodland, who poured in 11 birdies in a valiant final-round charge to a 63.

The in-form Koepka, who this year won his second US Open Championship and the US PGA title, shook off some shaky moments early in his final round at the Club at Nine Bridges on the southern resort island of Jeju.

He started the week ranked third behind Johnson and Rose, who both sat out the tournament, and will leapfrog the pair when the new rankings are officially announced on Monday. 

Koepka started his final round with a four-stroke lead over fellow American Scott Piercy and England’s Ian Poulter. But it was Woodland who emerged as Koepka’s nearest challenger.

Woodland began five shots adrift of Koepka, but four consecutive birdies from the sixth put him into a share of the lead at 14-under by the turn as Koepka traded three birdies with two bogeys on his front nine.

Woodland blinked first with a bogey at the 10th, and Koepka birdied that hole minutes later to reopen a two-shot lead.

Woodland bounced back with two straight birdies at the 12th and 13th, but Koepka matched the feat to maintain his advantage.

Both birdied the 15th. After Woodland had another birdie at the 16th, Koepka, now clinging to a one-shot lead, put his approach to the same par-four hole into the right rough.

With the potential for a bogey looming, Koepka chipped in for a thrilling birdie to reach 19-under.

Moments later, Woodland bogeyed the 17th to fall three strokes behind.

His birdie at the 18th wasn’t enough, as Koepka’s eagle capped off the victory in style.