Brooks Koepka retained his US PGA Championship title in dramatic fashion, triumphing by two strokes from Dustin Johnson after a stunning back-nine collapse at Bethpage Black.

Having been six clear with eight holes to play, Koepka paid the price for a succession of wild tee shots as he bogeyed the 11th, 12th, 13th and 14th amid rising winds, cutting his advantage to a solitary stroke with Johnson having birdied the 15th up ahead.

However, Johnson then wobbled himself, dropping shots at the 16th and 17th to significantly ease the pressure on his fellow American on Sunday.

And although Koepka made yet another bogey on the penultimate hole before finding trouble off the 18th tee, a closing par ensured he became the first man to retain both the Wanamaker Trophy and the U.S. Open, which he will seek to defend at Pebble Beach next month.

Koepka finished the week at eight under after a closing 74. Now firmly established as the dominant figure in golf, the new world number one's last five major appearances have yielded three wins and a second-place finish at last month's Masters. In addition, his haul of four major victories is bettered only by Phil Mickelson (5) and Tiger Woods (15) among active players.

He is only the fifth man to complete a wire-to-wire victory in the PGA Championship and the first since Hal Sutton in 1983.

Johnson, who carded a 69 to ensure he broke par in every round, has now finished second in all four majors, while Jordan Spieth shared third with Patrick Cantlay and Matt Wallace at two under to claim his first top-10 finish since last year's Open Championship. Luke List, one under for the week, was the only other player to break par.

Although Koepka - who seized control of this championship with opening rounds of 63 and 65 - was not at his best on the front nine, his distance control on the greens was exceptional and he looked firmly in control despite Johnson turning in 32 to close within four.

The lead was back up to six when Koepka made a superb birdie at the 10th but his game swiftly unravelled thereafter, as gusting winds made a challenging course even more difficult.

When a Johnson birdie at 15 – his fourth of the week at the hole – was followed by Koepka recording his fourth bogey in a row at 14, there was suddenly only one shot separating the top two.

Johnson could not keep the hammer down, though, and his errors over the closing holes in an otherwise outstanding round ultimately proved costly as Koepka did just enough to enhance his remarkable record in majors.

Harold Varner III, playing alongside Koepka in the final group, birdied the first only to then fall apart. An 81 left him way down the leaderboard in 36th.

One of the loudest roars on the final day was generated by Lucas Bjerregaard as the Dane made a hole-in-one at the 17th, the only ace of the week.