A week that began with Tiger Woods making his highly anticipated return to competition ended on Sunday when Phil Mickelson wrapped up an emotional three-shot victory at the US Masters.

The American left-hander birdied four of the last seven holes to win his fourth major title, and a third Green Jacket, in front of huge galleries that included his wife Amy and three children.

A stroke behind pacesetting Briton Lee Westwood overnight, Mickelson fired a flawless five-under-par 67 in the year's opening major to post a 16-under total of 272 at a sun-splashed Augusta National.

Cheered on by the crowds as he walked up the 18th fairway, the popular World No 3 put the seal on a heart-warming win with a 10-foot birdie putt at the last.

He thrust both arms skywards in triumph before hugging his caddie Jim Mackay and he then walked off the green to embrace his wife, who was diagnosed with breast cancer last year.

"This has been a very special day and a very special week," a beaming Mickelson said after being helped into the Green Jacket by 2009 champion Angel Cabrera of Argentina.

"To have Amy and my kids here to share it with, I can't put into words. It just feels incredible, especially given what we've been through in the last year."

"To be able to share this kind of joy means a lot to us," added the American, who was dressed entirely in black with a pink ribbon stitched on to his cap to promote breast cancer awareness.

Westwood, who had been seeking his maiden major title and Britain's first since Paul Lawrie won the 1999 British Open, finished in second after carding a 71.

American Anthony Kim closed with a sparkling 65 to finish third at 12 under, a stroke in front of World No1 Woods and KJ Choi of South Korea, who returned matching 69s.

"I am a little bit disappointed because I came so close to winning the tournament," said Westwood, who had tied for third in his two previous majors and trailed Mickelson by one at the turn. "I didn't get off to a fast enough start today.

"Phil hit some good shots around Amen Corner and they are not easy shots that he has pulled off there so he is a deserving winner."

Mickelson, who won his first two Masters crowns in 2004 and 2006, effectively wrapped up the title with back-to-back birdies from the par-three 12th, where he rolled in a curling 14-footer.

He narrowly missed an eagle from just three feet at the par-five 13th, after hitting a stunning blow with a six-iron from 207 yards through a four-foot gap between two pine trees, before holing out from a similar distance coming back.

That put him two strokes clear before he picked up another shot at the par-five 15th, where he reached the green in two and two-putted, to tighten his grip on a third Green Jacket.

"When I get here to Augusta, I get very relaxed and feel very comfortable," said Mickelson, whose fourth major title puts him one ahead of Ernie Els, Vijay Singh and Padraig Harrington and behind only Woods in the modern era.

Kim began another calm, sunny day at Augusta seven strokes off the pace but he surged into contention with a sizzling birdie-birdie-eagle-birdie run from the 13th.

Choi, aiming to become only the second Asian male to win a major after compatriot at Yang Yong-eun last year's PGA Championship, briefly joined Mickelson in a share of the lead before slipping back with bogeys on 13 and 14.

Four-times champion Woods, playing his first event in nearly five months following startling revelations at the end of last year about his serial philandering, endured a roller-coaster day.

He started out poorly with three bogeys in the first five holes before holing out from the fairway to eagle the seventh and then recording birdies at eight and nine.

After mixing bogeys at the 11th and 14th with a birdie at the 13th, he collected another eagle when he coaxed in a 15-footer at the par-five 15th before signing off with a six-foot birdie putt at the last.

"I finished fourth, not what I wanted," said Woods, who came under intense scrutiny from the fans and media all week. "I wanted to win this tournament.

"As the week went on, I kept hitting the ball worse."

Asked when he was likely to return to the PGA Tour, he replied: "I'm going to take a little time off and kind of re-evaluate things."