Keegan Bradley held his nerve at the first play-off hole to beat Ryan Palmer to the Byron Nelson Championship.
Bradley, who missed a 10-foot putt on the 18th in regulation, holed out from two feet in the play-off after Palmer made a bogey.
However, Palmer at least had the consolation that his performance in Texas sealed a berth at the Open.
Sergio Garcia, who led after 36 holes, could have qualified for Sandwich with a win, but finished in a tie for 20th.
"I don't know what to say. I'm so happy, I can't believe this just happened," said Bradley, whose victory came nine days before his 25th birthday.
"This is a dream come true. I've waited for this my whole life."
Palmer, who had forced the play-off with a rare birdie at the final hole of regulation, hit his approach shot into the water at the play-off hole and while he salvaged a bogey with a 13-foot putt it was not enough.
American Palmer closed with a two-over 72 to join Bradley on a three-under 277, the highest winning total on the US Tour in 2011, thanks in large part to the gusting winds that bedevilled the golfers over the final two rounds.
Given the conditions, Bradley's round was relatively uneventful, with birdies at the third, seventh and 10th and a bogey at the fourth. He saved par at the 172-yard 17th by draining a 12-footer.
Japan's Ryuji Imada exemplified the difficulty of the day.
Imada had a two-stroke lead after making a 10-footer for a birdie at 13 but he bogeyed three of the last four holes.
His short miss at the par-three 17th resulted in him moving into a tie for the lead, while his bogey at 18 cost him a place in the play-off.
Imada shot a one-over 71 for 278 and tied with American Joe Ogilvie, who posted a 70.
Australian Jason Day, the defending champion, carded a 67 for 279 - the last of only five players to finish under par for the week.