Jerry Kelly carded a seven-under-par 65 to dramatically capture the Advil Western Open in Illinois.
The 35-year-old from Wisconsin overturned a three-stroke deficit at the start of the day to record his second victory of 2002.
Kelly, who also captured the season-opening Sony Open in Hawaii, began the day tied for third, but produced a superb round to end the day two strokes ahead of Davis Love III.
He registered eight birdies and just one bogey to post a winning total of 19-under 269, breaking 70 in all four rounds.
He said afterwards: "I wanted to be me out there. I didn't try and do anything special and I knew what I had to do with my game.
"I had always talked about the Milwaukee Open and the Western being the biggest non-major tournaments that there are. There's no question about it. It doesn't get any better."
Love III began the day four shots behind leader Robert Allenby, and was also impressive in carding a six-under 66 to finish two strokes ahead of Brandt Jobe, who also shot a 66.
John Cook finished fourth at 274, one stroke ahead of Australian rookie Peter Lonard, Stuart Appleby, Duffy Waldorf, Chris Riley and Neal Lancaster.
Allenby saw his title bid slide away, shooting a three-over 75 to end in a three-way tie for 10th.