World number one Dustin Johnson capped a two-under-par 68 with a birdie at the last to seal a three-stroke victory in the US PGA Tour Championship and earn the $15 million FedEx Cup playoff title on Sunday.

Johnson finished with a 21-under-par total at East Lake Golf Club in Atlanta -- three shots clear of Americans Xander Schauffele and Justin Thomas.

"I hit the fairways when I needed to coming down the stretch," said Johnson, who started the day with a five-shot lead.

He rolled in an 18-foot birdie putt at the third, a 10-footer at the fifth and a three-footer at the sixth.

But bogeys at the seventh and eighth -- where he was in a fairway bunker -- opened the door just a crack for Thomas and Schauffele.

Neither could do enough, never getting the deficit below two strokes as Johnson parred nine straight.

That run included a 21-foot par-saving putt at the 13th, where he was in the left rough off the tee and right of the green and hit a poor chip but drained the putt to push his lead back to three over Schauffele.

"He made that putt, which I didn't," said Schauffele, who bogeyed the 13th. "That was a pinnacle moment, I think."

"Obviously it's a very tough trophy to win. This time I did control my own destiny, I knew what I had to do.

"But I still had to go out and play well today. I had a lot of great players right behind me and they played some good golf today. I knew I was going to have to come down the stretch and hit some golf shots."

He was in the fairway at the par-five 18th, but his approach hit the bank in front of the green and bounced back into the greenside bunker. He blasted out to five feet and made the putt for a closing birdie.

The 36-year-old claimed his 23rd US PGA Tour title and his third since the tour resumed in June after a three-month coronavirus shutdown.

He's the first overall points leader since 2009 to win the season-ending showdown for the $15 million (12.6 million euro) playoff prize.

World number one Dustin Johnson celebrates on the 18th green after winning the US PGA Tour Championship and the $15 million FedEx Cup playoff crown
World number one Dustin Johnson celebrates on the 18th green after winning the US PGA Tour Championship and the $15 million FedEx Cup playoff crown GETTY IMAGES NORTH AMERICA / Kevin C. Cox

Johnson had a head start coming into Eastlake. He began the week on 10-under thanks to his season points edge.

Spain's second-ranked Jon Rahm was next on 8-under with third-ranked Thomas on 7-under and others up to 10 shots adrift in the staggered start system.

Rahm, who edged Johnson in a playoff at the BMW Championship a week earlier, finished alone in third on 17-under after closing with his second straight 66.

Schauffele actually had the week's lowest 72-hole total of 15-under 265, but under the staggered start format he started the week seven adrift.

Johnson played 72 holes in 11-under 269.

Prior to his dramatic near miss at the BMW Championship, Johnson won the Northern Trust by 11 strokes to seize the world number one ranking.

In June, he won the Travelers Championship -- his first title since February 2019.

"I'm definitely playing probably the best I've ever played," the 2016 US Open champion said. "I really feel like everything is dialed in pretty well."

The Tour Championship marked the official end of the US tour's pandemic-disrupted 2019-2020 season.

The 2020-21 season starts this week with the Safeway Open, and while Johnson won't be there he and the world's other top golfers won't be settling down for some rest with the rescheduled US Open coming up at Winged Foot September 17-20.

"You've only got a few days," Johnson said.