Mike Weir beat Len Mattiace at the first hole of a sudden-death play-off to win the green jacket at Augusta on Sunday.
The 32-year-old Weir becomes the first Canadian to win a Major, and the first left-hander to take the US Masters.
"It's an unbelievable feeling," said Weir as he was presented with his green jacket by defending champion Tiger Woods.
"It's something I've dreamt about for a long time and worked very hard for it. It's a thrill and tough for me to put into words because I wouldn't do it justice."
Tied at seven under par after 72 holes of enthralling golf, Weir and Mattiace went back to the par-four 10th hole to settle the first Major of the year.
Both players found the fairway but Mattiace pulled his approach shot into the trees to the left of the green.
Weir then found the putting surface with his second shot, 40 feet short of the pin.
Mattiace chipped well past the hole but was given hope when Weir ran his first putt eight feet past.
But Mattiace pushed his putt 15ft past the hole and missed the return, leaving Weir two putts to win the title.
Weir, the first left-hander to win a Major since New Zealand's Bob Charles triumphed at the 1963 Open, carded a 68 in Sunday's final group, while Mattiace fired a seven-under-par 65, the lowest round of the day.
The 35-year-old American, a journeyman for most of his career until two wins last year, had reached eight under par only to bogey the 18th.
It was still a remarkable effort from the New Yorker, who had made only one previous appearance at Augusta, missing the cut in 1988 as an amateur.
While Mattiace was struggling with his nerves on the final hole, Weir played a stunning chip shot to the par-five 15th to set up a birdie that took him to seven under.
Weir then had to hole a six-foot putt at the last to force the play-off, but it was no surprise when he did so as his putting was excellent throughout the tournament.
Phil Mickelson finished third at Augusta for the third year running after carding a 68, while Tiger Woods, who had been chasing an unprecedented third straight Masters, could only manage a 75 and a share of 15th at two-over 290.
American Jim Furyk, who closed with a 68, secured fourth at four under, and third-round leader Jeff Maggert fought back from a triple-bogey at the par-four third to card a 75 for fifth place at two under.