Viktor Hovland has played the best golf of his life in the final two weeks of the PGA Tour season, and it paid off with the biggest trophy of his career.

Starting the final round of the season-ending Tour Championship with a six-shot lead, Hovland didn't flinch under a relentless challenge from Xander Schauffele.

By the end of Sunday, the Norwegian had clinched the FedEx Cup title and with it a cheque for $US18 million ($A28 million).

The 25-year-old Hovland stayed on the attack and closed with a seven-under 63 for a five-shot victory at East Lake in Atlanta, Georgia.

"It's pretty surreal to be standing here right now," Hovland said.

"I played basically my best golf the last two weeks and it couldn't have happened at a better moment."

Schauffele (62) made him work for it and got to within three shots with seven holes to play. 

Hovland ended the suspense with a 25-foot par putt on the 14th hole, and put Schauffele away with a birdie on the 16th.

Schauffele and Hovland put on a superb show. Playing in the last group after a delay of nearly two hours caused by thunderstorms, they had the best scores of the day.

Schauffele did everything he could. He was six shots behind when he left East Lake on Saturday evening, knowing his only hope was to put as much pressure on Hovland as he could over the front nine.

The American shot 30. Hovland nearly matched him birdie for birdie, posting a 31 that included a key 15-foot par save on No.2.

Schauffele, for all his California chill, was simply relentless. He holed an 18-foot birdie putt on the par-3 11th and followed with a 12-foot birdie on the 12th, cutting the lead to three shots with seven to play.

The putt that mattered came at the 14th, the toughest hole at East Lake.

Hovland came up short of the green, about 100 feet from the flag, and his pitch was weak and stopped just inside 25 feet from the hole.

He poured it in the heart and pumped his fist stronger than he had all day.

The clincher was another pure short iron, this one to 10 feet on the 16th for birdie.

At that point, the engraver went to work on the silver FedEx Cup trophy.

"I thought 62 would have let me get close to him," Schauffele said.

"He played unbelievably well. He made important putts and he's just played like a champ.

"I'll hold my head up high. It was the most fun I had losing in quite some time. It's such a weird feeling. I shot 62. I lost by five."

Australia's Jason Day finished with a final-round three-over 73 to end in 28th place.