Nick Dunlap kept his cool to become the first amateur to win a PGA Tour event since Phil Mickelson in 1991.
The 20-year-old sank a six-foot putt at the last to win the American Express title by one stroke ahead of South Africa’s Christiaan Bezuidenhout.
It was his fourth PGA Tour event after missing the cut in his previous three.
“It’s so cool to experience this as an amateur,” said the emotional American after being embraced by his parents in California.
“Whether I made it or missed it, if you had told me Wednesday night that I had a putt to win this tournament, I wouldn’t have believed you.”
Mickelson, a six-time major winner, posted on X: “Such an impressive performance from Nick Dunlap. Congratulations on an incredible victory.”
Dunlap is only the seventh amateur to win a PGA Tour event, but his stock is already high after imitating Tiger Woods last year to become the second player to win both the US Junior Amateur and US Amateur titles.
His final round at the Pete Dye Stadium Course in La Quinta featured a double-bogey six after sinking his ball into a lake on the seventh as he saw his three-shot overnight lead evaporate.
But the University of Alabama student responded magnificently with three birdies in his next nine holes as he closed with a two-under 70 to hold off a charging Bezuidenhout.
The South African, who holed a 138-yard corner shot for an eagle two on the par-four 15th, also birdied the last in a seven-under 65 to set a clubhouse target of 28 below.
Dunlap, who moved to 29 under with a birdie at the 16th, admitted he was unaware of Bezuidenhout’s birdie on the final hole and when he stood over his second shot at the last he thought have a two-shot lead.
His approach fled to the right and hit a spectator before coming to rest a few meters from the edge of the green. And he climbed up to six feet and made the putt without any nerves after his caddy told him “it’s inside left, you’ve made a million of those before.”
Because he is an amateur, Dunlap will not receive any prize money, with the winner’s check for $1.5 million (£1.18 million) going to Bezuidenhout.
And when asked if the natural next step was to turn professional, he said: “I don’t know. I have to take a second to let what just happened sink in a little bit.
“It’s a decision that doesn’t just affect me. It affects a lot of people, and obviously I’m going to try to take advantage of it.”
