Jordan Gumberg started the day three shots off the lead at the SDC Championship but carded a bogey-free 68 to reach 12-under and enter a playoff against South African Robin Williams.
Williams had held the lead for most of the day but a double bogey at the par-3 17th denied him the victory.
Both players parred the first extra hole but Gumberg birdied the second to win his first DP World Tour title while Williams parred.
"It means everything. I never really got this far in my dreams. So I'm kind of at a loss for words but it means everything," said the American.
"It's what we fight for every day, it's what we practise for, it's the early hours, the late hours, everything. This is incredible.
"I want to thank my fiancée, first and foremost, she's amazing. I wouldn't be here without her. And my family back home. My dad has put so much into my golf game and just to be standing here for him and my mum and everybody just means the world."
France's David Ravetto closed with a 70 to take solo third place at 10-under.
Overnight co-leader Daniel Brown fired just one birdie and suffered four bogeys to close with a 75 and finished in a tie for fourth place at 8-under alongside fellow Englishman Andy Sullivan whose 73 featured five birdies, two bogeys and two double bogeys at the par-3 4th and the par-4 10th.
Also tied in fourth place are Scotland's Connor Syme who started the day with a share of the lead but made two birdies, three bogeys and a double bogey at the par-3 14th for a 75, as well as Germany's Nick Bachem who shot four birdies and three bogeys for a 71.
England's Marcus Armitage signed for a 70 and Wales' Jamie Donaldson for a 68 to join them in fourth place.
