Shane Lowry carded a 5-under 66 on Sunday to win the Portugal Masters by a single stroke.
Lowry finished at 14-under 270 and locked up his first European Tour win as a professional when Ross Fisher's par putt on No. 18 rimmed out.
"I'd be lying if I told you I wasn't nervous," said Lowry. "I just trusted myself and trusted my game...that it was good enough to be a winner."
Fisher, who hasn't won since capturing the Irish Open in 2010, shot 70 on Sunday to place second, while Michael Campbell (68) grabbed third place at 12- under. Third-round leader Bernd Wiesberger slipped to fourth at 11-under with a final-round 73.
Lowry's only other tour victory came in 2009, when he won the Irish Open as an amateur. With Sunday's triumph, the Irishman became just the second player to win on the European Tour as both a amateur and a professional -- Pablo Martin was the other.
Sunday's 66 proved to be Lowry's low round of the tournament. He entered the final day three shots off Wiesberger's pace, but battled into contention with the aide of an eagle on the par-four 11th.
Lowry recorded the two with a 7-iron from the fairway, then added birdies on 15 and 17 to take a 1-stroke lead. He found a bunker on the last and settled for a bogey as Fisher was set to tee off.
Fisher, who suffered a sprained ankle on Friday, found the fringe in two before leaving his long birdie putt five feet short. The Englishman failed to force a playoff when his next attempt lipped around the edge of the cup as an onlooking Lowry celebrated.
"I knew I had a chance going out there today and I went out and gave it my all," said Lowry. "I played one shot at a time and managed to play a few good ones. To be standing on the 18th green with the trophy in my hands was a bit surreal."
It proved a familiar scene for Fisher, who recorded three bogeys on Saturday, including one on the last, which allowed Wiesberger to go in front.
"(I'm) disappointed with the way I finished, but you win some and you lose some," said Fisher, who sprained his left ankle while taking his first shot of the second round.
"If someone would have told me after I walked off the first tee on Friday that I was going to have a putt to get in a playoff I would've bitten their hand off because I really didn't think I was going to make it," he continued.
Seeking his third European Tour win of the season, Wiesberger shot a second- round 65 at the Oceanico Victoria Golf Course to go in front. He couldn't maintain the momentum, however, and carded four bogeys to go with a pair of birdies on Sunday to fall off the pace.
NOTES: Tom Lewis, the 2011 champion, shot 69 on Sunday and finished in a tie for 49th place at 3-under...Ryder Cup victor Francesco Molinari tied for 16th at 6-under...This was the final tournament to be played in Europe for 2012. The next time the tour will play on European soil is April, 2013.