Dustin Johnson held off determined challenges from Justin Thomas and Xander Schauffele to win the Tour Championship, FedEx Cup title and the first prize of $15m (€12.7m) in Atlanta.

Johnson saw his five-shot overnight lead cut to two, first by playing partner Schauffele and then Thomas, but the world number one held his nerve to secure the eight-figure payday at East Lake.

A closing round of 68 gave Johnson a winning total of 21 under par, with Schauffele and Thomas sharing second place on 18 under following matching rounds of 66.

Defending champion Rory McIlroy, who celebrated becoming a father for the first time with the birth of daughter Poppy a week ago, carded five birdies and two bogeys in a closing 67 that left him in a tie for eighth place and earned him just under a million dollars.

Johnson told the Golf Channel: "This is a difficult golf course so no lead is really safe. I knew I was going to have to come out and play really well.

"I got off to a really good start, missed a couple of putts on the back side but hit the fairways when I needed to coming down the stretch. The guys gave me a good fight today.

"I wanted to be a FedEx Cup champion, it's something in my career I would like to be and I’m very proud of the way I’ve played, especially over the last four tournaments."

It was the fourth event in a row in which Johnson had led or shared the lead after 54 holes, aided by starting on 10 under par thanks to the controversial handicap system adopted last year for the FedEx Cup play-offs.

The 36-year-old finished second in the US PGA Championship, shot 30 under par to win the first play-off event by 11 shots and then lost a play-off in the BMW Championship, where Jon Rahm holed from 66 feet for birdie on the first extra hole.

Unsurprisingly, the last player to hold the 54-hole lead in four straight strokeplay events was Tiger Woods in 1999 and he won all four, starting with the US PGA Championship and ending with the Tour Championship.

Johnson's five-shot lead made him a prohibitive favourite for victory and he responded to a flurry of early birdies from his rivals with three of his own in the first six holes.

Bogeys at the seventh and eighth gave the chasing pack hope and Schauffele birdied the 11th and 12th to get to within two of the lead as Johnson began to feel the pressure.

However, just when he had Johnson on the ropes, Schauffele let him off again with a bogey on the 13th after pushing his drive into the trees and fluffing his pitch from short of the green.

Johnson had also come up short of the green and hit a similarly bad pitch, but rattled in the par putt from 20 feet to extend his lead once more.

Schauffele got up and down from 130 yards to save par on the 14th following another errant drive and Thomas birdied the 16th to close within two of Johnson’s lead, only to promptly bogey the next after a wild tee shot.

Schauffele also birdied the 16th to keep the pressure on Johnson, but that was as close as he could get and Johnson finished in style with a birdie on the last.