Frenchman Jean-Francois Lucquin defeated 19-year-old Northern Irishman Rory McIlroy at the Omega European Masters on the second hole of a play-off at Crans-sur-Sierre in Switzerland.
Aussie Brett Rumford (five-under) finished eight strokes adrift of McIlroy and Lucquin (13-under) in a share of 23rd position.
McIlroy was a five-foot putt away from becoming the third youngest winner in European Tour history - and then saw it all go horribly wrong.
After McIlroy's par attempt on the 72nd hole had failed and he had angrily thrown his ball into the water by the green, the teenager had another chance to take the title at the start of sudden death.
However, his 15-foot attempt missed as well and, hard though it was to believe, worse was to follow.
Playing the 405-yard 18th for the third time he hit a 25-foot birdie putt 18 inches past the cup and incredibly missed that too.
Lucquin, 12 feet away, suddenly had victory in his grasp.
The 29-year-old, who actually lives in Switzerland, was ranked 460th in the world at the start of the week and at 127th on the Order of Merit was fighting for his future.
Now he has a two-year exemption on the circuit and is 268,010 pounds ($AU 575,853) richer.
For McIlroy the runners-up cheque for 178,673 pounds ($AU 383,969) - plus a 3500-pound ($AU 7521) watch for his first round 63 on Thursday (UK time) - was little consolation.
Only South African Dale Hayes and Spain's Seve Ballesteros had won at a younger age.
"Obviously I am very disappointed," he said. "I got very unlucky on the 18th in regulation, where it got a pretty big bounce for a sand wedge."
"I hit a good chip, but not a very good putt. Then second time around in the play-off it didn't really matter as he holed his."
"That made me feel a bit better after missing that putt. I can take a lot from this week - I played very well all week and played well coming down the stretch, but unfortunately one bad shot cost me."
"I came here after three missed cuts in a row and found a bit of form. It would have been nice to go home with the trophy, but I have plenty more tournaments even this year."
"It would be great to get a win this year, but if not I have the rest of my career. C'est la vie."
He had been four clear with a round to play, but after bogeys at the second and third suddenly found himself one behind and then down to fourth place at one point.
However, last year's leading amateur at The Open came back from that and moved one ahead again by sinking a 20-foot birdie putt at the long 15th.
By getting down in a chip and a putt on the next two holes he stood on the last needing another par for the trophy.
Going over the green gave Lucquin hope, though, and after his chip had run just past the edge of the hole he was one shot from glory. But 11 shots later it was all over and he was the loser.
The pair had tied on the 13-under-par total of 271, Lucquin closing with a 67 to McIlroy's bitterly disappointing level-par 71.
Joint third only one behind were Ryder Cup Spaniard Miguel Angel Jimenez, Scot Gary Orr, Swiss player Julien Clement and another Frenchman,