ATLANTA -- Dustin Johnson hit his stride at just the right time, and it paid off in a big way.

Johnson finally won the FedEx Cup on Monday by holding his nerve, hitting just enough fairways and making a few key putts when his lead began to shrink. He tapped in for birdie on the last hole for a 2-under 68, giving him a 3-shot victory over Justin Thomas and Xander Schauffele in the Tour Championship.

Johnson won the $15 million prize, the biggest in golf. Equally important was getting his name etched on that silver FedEx Cup trophy alongside some of the best of his generation, starting with Tiger Woods and most recently Rory McIlroy.

"This is a tough golf course. No lead is safe," Johnson said. "The guys gave me a good fight today."

Johnson became the first No. 1 seed at the Tour Championship to win the FedEx Cup since Tiger Woods in 2009.

Johnson was staked to a 5-shot lead at 19 under par -- 9 under on his own score and starting the tournament at 10 under as the No. 1 seed in the FedEx Cup.

He finished at 21 under.

Schauffele, who tends to bring his best to big moments, and Thomas each got within 3 shots on the front nine. They both closed to within 2 shots deep on the back nine at East Lake.

Johnson gave the lightest fist pump -- that's big emotion for him -- when he holed a 20-foot par putt on the 13th hole that kept his lead at three. He made nothing but pars on the back nine until the outcome was no longer in doubt.

Thomas made bogey from a wild tee shot to the right on the 17th. Schauffele also had to scramble on the 17th, escaping with par after a tee shot into the bunker. On the par-5 18th, Johnson unleashed a drive that started left along the pine trees and faded gently toward the middle of the fairway.

That set up a birdie from the front bunker, a hug with brother Austin, his caddie, and a trophy Johnson long wanted.

Schauffele had the lowest score over 72 holes at 15-under 265, but without a victory this year, he started at No. 14 in the FedEx Cup, spotting the world's No. 1 player seven shots.

Schauffele and Thomas tied for second, each earning $4.5 million.

Jon Rahm, the No. 2 seed, closed with a 66 to finish fourth and earn $3 million. Scottie Scheffler, who a year ago was getting ready to start his rookie year, had a 66-65 finish and was fifth for a $2.5 million payoff.

Thus wrapped up the strangest season on the PGA Tour. It doesn't seem like the end at all, except for the $15 million awarded to Johnson -- $14 million now and $1 million deferred.

The new season starts Thursday. Two majors are still to be played.

Golf was shut down for three months, and when it restarted, Johnson was No. 111 in the FedEx Cup. He won the Travelers Championship, and a month later began a stretch that brought him to the prize he desperately wanted.

In four straight tournaments against the best fields, he had the 54-hole lead three times and was tied in the other. He converted one into an 11-shot win. He lost to a 65 by Collin Morikawa at the PGA Championship and to a 65-foot putt by Rahm at the BMW Championship.

He badly wanted the last one, but even staked to a 5-shot lead to par at East Lake, it was never easy.

Johnson made an 18-foot birdie early that was important because Schauffele kept hitting it close. Johnson had consecutive birdies through the par-5 sixth, and his lead remained at 5.

But he went well right off the tee at No. 7 and had to pitch back to the fairway. He three-putted from 55 feet on the fringe at No. 8 and dropped another shot. The lead kept shrinking. Johnson rolled his long birdie putt on the par-3 ninth some 7 feet by, and he made the par putt coming back to keep his lead at 3.

No putt was bigger than the 13th, when his lead was down to 2 shots over Schauffele. Johnson went from left rough to right of the green and chipped weakly to 20 feet. He drilled the par putt, restored the lead to 3 and was on his way.

"It's a very tough trophy to win," Johnson said. "I controlled my own destiny, but I still had to go out and play well. I had a lot of great players right behind me. It got close at the end. I knew it was going to come down the stretch, and I'd have to hit some golf shots."