Ireland's Shane Lowry held off the challenge of three major champions to claim the biggest victory of his career in brilliant fashion in the WGC-Bridgestone Invitational.

Lowry carded a flawless final round of 66 at Firestone Country Club to finish 11-under-par, two shots ahead of double Masters champion Bubba Watson, with Justin Rose and Jim Furyk another two shots back after disappointing rounds of 72.

"It's hard to believe but I played good today," Lowry said. "I was quite nervous out there towards the end but made a lot of good decisions, hit the ball well and got a bit of luck as well which was nice.

"It's great to be able to pull something off. I was kind of doubting myself a little this year, things haven't been going my way but when you come out the other end it's always nice."

Lowry began the final round two shots off the lead shared by former US Open champions Rose and Furyk, but wiped out the deficit with birdies on the second and eighth.

And when he produced a spectacular recovery following a wayward tee shot on the 10th, the resulting tap-in birdie gave the 28-year-old a two-shot lead over the chasing pack.

Watson then recorded his fourth birdie in six holes on the 13th to close within a shot and Furyk did likewise with a birdie on the 11th, only to promptly bogey the next after chipping from one side of the green off the other.

And when Watson also dropped a shot on the 15th, Lowry was two in front again and maintained that advantage with a superb par save from 20 feet on the 14th after finding a fairway bunker off the tee.

"That was massive," Lowry admitted. "The bunker was pretty dead and even with my pitch I could not go at the flag and just had to hope to hole a long putt."

Watson closed within a shot once more thanks to a brilliant birdie on the 17th, following a wild drive with a superb approach up and over a tree to within seven feet of the hole.

A drive of 379 yards down the 18th gave Watson the chance of another birdie, but this time his approach finished 25 feet from the hole and the left-hander had to settle for par.

The resulting 66 set the clubhouse target at nine under par and left Lowry needing to par the final two holes for victory. He held his nerve to hole from five feet on the 17th but looked to be in trouble when he pulled his tee shot on the last into the trees.

However, the former Irish Open champion - he was still an amateur when he won the title in 2009 - found a good lie in the rough and powered a wedge over the trees to 11 feet, from where he holed for a birdie to make certain of the first prize of 1,570,000 US dollars.

"I was trying to get it on the front right of the green but pulled it a little bit, it went through the tree and rest is history," Lowry added.

Scotland's Marc Warren finished on level par, while Stephen Gallacher was eight-over.