Believing his only chance to capture the PGA Tour money title was to win at Disney, Donald ran off six straight birdies on the back nine Sunday and closed with an 8-under 64 to come from five shots off the lead and win the Children's Miracle Network Classic.
'This is one of the most satisfying wins of my career,' Donald said.
Donald, who trailed Webb Simpson by $363,029 coming into the final tournament of the year, was two behind Simpson when they made the turn. Then came a performance that ranks among Donald's best, even in his greatest season of golf.
He holed four straight birdie putts inside 8 feet, took the lead with an 18-foot birdie on the par-5 14th hole, then sealed his stunning rally with a 45-foot birdie on the 15th hole.
'Everything was on the line,' Donald said. 'I'm thrilled and over the moon.'
It was his second PGA Tour win of the year. Donald also won the Vardon Trophy for the lowest adjusted scoring average. With no one else winning more than twice this year, Donald established himself as a heavy favorite to be PGA Tour player of the year.
The award is a vote of the players, and ballots go out on next week.
'We gave ourselves a chance,' Simpson said. 'The fact is, playing against the best player in the world, he's going to do something great like that most of the time, and he did. Made six birdies in a row. Tough to compete against.'
As for player of the year?
'I don't know yet,' said Simpson, who won twice and was No. 2 on the money list and the FedEx Cup. 'I think I've played great. Luke has played great. Couple other guys have played well. Still probably up in the air a little bit. But I'm sure I'll vote for myself.'
Donald also kept alive his bid to become the first player to win the money title on the PGA Tour and European Tour in the same season. His lead in Europe is just over $1.8 million over Rory McIlroy with five tournaments remaining.
He wound up with a two-shot win over Justin Leonard, who finished with eight pars for a 71. Leonard already is exempt for next year, but kept alive his streak of never finishing out of the top 125 on the money list since joining the tour in 1994.
Donald finished at 17-under 271 and earned $846,000, giving him just over $6.6 million for the year. Simpson was runner-up on the money list, just as he was in the FedEx Cup.
Tom Pernice Jr., a 52-year-old who refuses to give up on playing with guys half his age, closed with a 69 for a three-way tie for third, earning enough money to finish at No. 121 and earn back his PGA Tour card.
There were plenty of twists and turns at the bottom of the money list, as players were grinding to finish in the top 125 to have full status on tour next year.
Bobby Gates missed a 6-foot putt on the final hole but still appeared safe. Pernice only moved into the top 125 when Nick O'Hern bogeyed his last hole and fell out of the logjam at third place. On the other side of the Magnolia Course, D.J. Trahan knocked in a 22-foot birdie putt on his last hole at No. 9 – the second-toughest hole.
That ultimately enabled Trahan to finish at No. 125 on the money list by $1,431 over Gates.
'I don't know what par would have done,' Trahan said. 'I really, honestly don't know what difference that would have made, but birdie certainly didn't hurt me. So I'm thrilled that I made that putt.'
Donald, however, stole the show.
He only entered Disney after Simpson decided to play at Sea Island last week, and when Simpson was the runner-up to take the lead on the money list, Donald knew his best chance was to win.
Never mind that he was five shots behind to start the final round. Or that it has been five years since he last won a stroke-play event on the PGA Tour. Over the next hour, Donald showed why he is No. 1 in the world.
He matched birdies with Simpson on the easy par-5 10th, and from there, Donald was in his own world. A wedge to 8 feet on the 11th. An 8-iron to 6 feet on the 12th. A lob wedge to 5 feet on the 13th.
The most meaningful shot came at the par-5 14th, where Donald had gone bogey and double bogey the previous two rounds, then pledged to reporters he would make birdie Sunday. He rolled in an 18-foot putt to get his revenge and take the lead. 'The putt on 15 was a bonus,' Donald said.
So was the reaction. For a man with so little emotion, Donald crouched, let out a yell, then slammed his fist toward the ground when the ball dropped into the center of the cup. Donald suddenly had a two-shot lead, and no one behind him was making a move.
His wife, Diane, is expecting their second child in just over a week. She was watching from home, and posted on Twitter, 'I don't think this much jumping up and down is good for the baby!!!'
Kevin Chappell, the PGA Tour rookie who shared the 54-hole lead with Leonard, was tied for the lead when he missed a 3-foot birdie putt on the 10th and dropped a shot on the 11th with an approach into the bunker. Chappell closed with a 72 and was in the group at 274 that included Pernice and Sunghoon Kang, who birdied the last hole and moved into the top 125.
'I'm just dreaming right now,' Kang said.
It felt that way for Donald, too, who has done nothing but prove skeptics wrong all year.