American Kevin Stadler finished with an eagle for the third day running to claim a two-shot victory at the Johnnie Walker Classic in Perth.
GB&I unless stated
-20 K Stadler (US)
-18 N O'Hern (Aus)
-16 R Green (Aus), R Allenby (Aus)
-15 KJ Choi (Kor)
-14 I Poulter, F Molinari (It), A Scott (Aus)
-13 F Couples (US)
-12 R Fisher
-11 P Casey
-9 St Webster
Stadler, the 26-year-old son of 1982 US Masters champion Craig, carded a final-round 69 to finish on 20 under.
Australian Nick O'Hern birdied the last two for a 68 and ended two shots back.
Robert Allenby and Richard Green both finished on 16 under, one ahead of KJ Choi, while Ian Poulter's 69 gave him a share of sixth place on 14 under.
Overnight leader Stadler teed off on the par-five 18th needing at least a birdie to win the event.
And a brilliant second shot to the green left him a simple one-foot putt to claim the biggest title of his career.
"That was the best shot I hit all week as I knew I had to make at least four, but thankfully I didn't have to worry about the putt," Stadler said.
"It was the perfect club to the perfect pin position."
The victory gave Stadler a two-year exemption from the Australasian, Asian and European Tours.
"I am honestly baffled by this win," he added.
"It was my intention this year just to play the Nationwide Tour and get my PGA Tour card back but now I have no idea what I will do.
"I just wanted to come down to Australia and get some golf under my belt in readiness for the two Nationwide events next week in Adelaide and then in New Zealand."
O'Hern, meanwhile, was gracious in defeat.
Searching to end a seven-year title drought, he narrowly missed an eagle putt of his own on the last but still finished to finish two shots clear of his compatriots Allenby and Green.
"I got off to a flyer to be three-under par after five holes but then I hit a brick wall," he said.
"With three holes to go, I figured I needed to birdie three of them but I could not believe my eagle putt at the last missed.
"If I had of holed that putt I might had a chance but it didn't happen. All credit to Kevin though, as he hit a great shot into the last."