Phil Mickelson missed a putt for a 58 but tapped in for 59 - the best score in professional strokeplay history - to win the Grand Slam of Golf in Hawaii.
-17 Phil Mickelson (US) 68 59
-12 Vijay Singh (Fij) 66 66
-11 Retief Goosen (SA) 65 68
+1 Todd Hamilton (US) 70 75
The Masters champion went out in 28 and bagged 11 birdies and one eagle to finish on 17 under for 36 holes.
Fiji's USPGA champion Vijay Singh, the world number one, was second on 12 under with South Africa's US Open winner Retief Goosen on 11 under.
Open champion Todd Hamilton carded a final-round 75 for one over in Kauai.
Mickelson had a 10-foot eagle putt on the 18th hole for an unprecedented 58 but the putt curved just left of the cup.
His 17-under total matched Tiger Woods' record score in the annual showdown for the winners of the year's four majors, and earned the left-handed Californian a first prize of $400,000.
The world number five's previous career low round was a 61 at the Greater Hartford Open in Connecticut in 2001.
The 34-year-old Mickelson admitted: "It feels like a fluke because I wasn't really that sharp, it just kind of all came together.
"I felt like this was a once-in-a-lifetime opportunity and I was glad when that last putt went in.
"When I made the putt on 16, I knew what was going on and I was really excited because I knew 18 was a birdie hole."
However, Mickelson added that he was not overly concerned with missing out on a 58.
He said: "To me, there's not much difference between a 58 and 59.
"But there's a huge difference between 59 and 60 - I
just wanted to make sure I only two-putted the 18th."
Singh, the world number one, said: "After about the 12th hole we were just watching him."
Only three other players have fired 59 on the PGA Tour - Al Geiberger in 1977, Chip Beck in 1991 and David Duval at the Bob Hope Chrysler Classic in 1999.
Sweden's Annika Sorenstam, the world's number one female golfer, shot 59 in the second round of the 2001 Standard Register on the LPGA Tour.