By Nick Mulvenney

SYDNEY (Reuters) - World number five Jordan Spieth showed major-winning class when it mattered by draining a 12-foot birdie putt to claim the Australian Open title for the second time after a three-way sudden death playoff on Sunday.

The American, who also lifted the Stonehaven Cup in 2014, shot a final three-under 69 to join Australian clubhouse leaders Ashley Hall and Cameron Smith, who both shot final round 66s, on 12-under-par for the tournament.

Replaying the par-four 18th hole in front of a packed gallery at Royal Sydney, Hall landed his approach shot closest but slid his birdie putt wide of the hole, while Smith gave himself too much to do with a second shot to 35 feet from the pin.

If his victory was not as convincing as that at The Australian Golf Club two years ago, when he shot a sizzling eight-under 63 in his final round, Spieth thought it was deserved.

"I felt I played really well this week," he said. "Certainly felt like I was playing well enough to be in contention, just wasn't sure about winning, and then we made the putts at the very end that mattered."

Hall and Smith will be rewarded for their second place with spots at next year's British Open along with Aaron Baddeley, who finished in a tie for fourth with four other players after a final-round 71.

Also in that group on 10-under was former U.S. Open champion and overnight leader Geoff Ogilvy, who held a three-shot lead at the eighth hole before a calamitous double bogey at the 16th ended his bid for a second title at his home open.

"I didn't have my golf swing all week really, to be fair," he said. "It was a tricky day and Sunday, if you've got anything in there that's not right, it gets exposed and it got exposed."

Former world number one Adam Scott was also looking for a second title but, after starting the day four shots off the pace, double-bogeyed the 11th then dropped another shot at the 12th to finish with a 73 and a share of 14th on six-under.

Spieth started the day with birdies at his first two holes but also hit trouble in the wind and had three bogeys with another birdie around the turn.

Two more birdies at the 12th and 13th brought him to within one shot of the lead and, as Ogilvy crumbled behind him, another after a lengthy putt at the 16th proved sufficient to get into the playoff.

The 23-year-old will be hoping his second Australian Open title will prove as much of a springboard as his first.

He followed up his 2014 triumph, his first professional win, by taking five titles, including the U.S. Masters and U.S. Open, in 2015.

Hall's priorities ahead of the majors this year are a little more prosaic, as the world number 902 explained when asked what his berth at Royal Birkdale meant to him.

"It's amazing and a big help with finding accommodation, flights and all sorts of stuff," he said.

"Finding a rental house near the course is a real pain, so knowing six months out you're in is a very big advantage."

(Editing by)