MARANA, February 24, 2014 (AFP) - Dubuisson had erased a three-hole deficit to extend the title match scheduled for 18 holes, and kept it going with two miraculous shots out of the desert cactus before Day finally sealed the win.
Day, 26, never trailed in the match after taking the lead with a birdie at the opening hole. But that fact hardly reflected the drama of the latter stages, when Dubuisson birdied the 17th and got up and down for par from a bunker at 18 to square the match as Day bogeyed 18.
The 23-year-old from Cannes, who won his first European Tour title at the Turkish Open in November, was in serious trouble at the 19th hole, where his approach shot bounced into the desert scrub and nestled in a clump of cactus.
He stepped up and took an unceremonious swing at it, sticking it six feet from the pin and making the putt to stay alive.
He hacked out of the scrub again at the 20th hole en route to a par that matched Day's.
At the 23rd, Dove Mountain's drivable par-four 15th, Dubuisson ran out of steam.
His drive bounced into thick rough and his chip out ran almost 30 feet past the pin.
Day was in the first cut of rough and chipped out to three feet.
Dubuisson's long birdie attempt was short and his par conceded before Day rolled in his winning putt -- it was the first hole Day had won since the ninth.
Day captured his second US PGA Tour title and his first in an elite World Golf Championships event. This week's $9 million tournament started with 64 players on Wednesday and as the last man standing Day collected $1.53 million.
Dubuisson earned $906,000 for his runner-up finish in his first WGC event.
In the consolation match, Rickie Fowler needed 19 holes to beat four-time major champion Ernie Els and claim third place.
The long day in the Arizona desert started with the semi-finals, in which Dubuisson defeated his onetime idol Els 1 up and Day downed Fowler 3 and 2.
Results on Sunday from the $9 million World Golf Championships Match Play Championship:
Championship final
Jason Day (AUS) bt Victor Dubuisson (FRA) 23 holes
Consolation final
Rickie Fowler (USA) bt Ernie Els (RSA) 19 holes
Semi-finals
Jason Day (AUS) bt Rickie Fowler (USA) 3 and 2
Victor Dubuisson (FRA) bt Ernie Els (RSA) 1 up