Carl Pettersson has backed up his tournament record 60 in round three by shooting a three-under 67 to take out the RBC Canadian Open.
The 32-year-old finished one stroke ahead of Dean Wilson to claim his fourth PGA Tour victory with Luke Donald third.
Overnight leader Wilson came into the last day with a four-stroke lead after three successive 65s had taken him to 15-under par, but a damaging 72 over the final round opened the door for Pettersson.
Australian Greg Chalmers finished in a large group that was tied for fourth, which included Matt Kuchar, Bryce Molder, Bob Estes and Tim Clark.
But the day belonged to the Swede Peterson who stormed home over the last two rounds to clinch the title.
"I still can't believe I won the tournament," Pettersson said.
"I know it's difficult to shoot another low one after a round like that, so I was just trying to downplay it."
"I just tried to stay calm and (said), `Whatever happens today, happens.'"
Six strokes behind Wilson after seven holes and four back with seven to play, Pettersson made a 15-foot birdie putt on the par-3 13th to pull within one, then took the lead with a 25-footer from the fringe on the 480-yard, par-4 14th.
Wilson bogeyed 14, hitting into the thick rough to the right of the green, chipping through the putting surface to the opposite fringe and missing a 15-foot par try.
"That was my bad swing of the day," Wilson said.
"I had a good yardage, good mindset on what I was going to do and I just didn't execute. I caught that ball a little thin and it rolled through the green. And I paid the price in that rough."
Pettersson pulled away on the par-5 15th with his third straight birdie and fourth in five holes, hitting a wedge to four feet.
Pettersson parred 16 and 17 and, with a shot to spare, bogeyed the 18th, missing a five foot par putt after Wilson putted out for his fourth straight par.
"I felt like I handled it well coming in," Pettersson said.
James Nitties, Stuart Appleby and Matt Jones were the next best of the Aussies, finishing in a tie for 37th spot at five under. Mark Hensby and Steve Elkington were tied for 48th, a further shot back.