Englishman Tom Lewis birdied five of the last seven holes to win his maiden title at the Portugal Masters, in only his third professional start.
The 20-year-old, who shot to fame by leading The Open as an amateur in July, beat a field that included Padraig Harrington and Martin Kaymer.
Lewis shot a closing 65 to finish with a 21-under-par 267 to claim the £375,000 first prize.
"If you said that I'd finish 21 under, I'd have said 'no way'," he said.
"I'm a long way behind Rory [McIlroy] in the Order of Merit so I've got a long way to go. But I'm really pleased.
"To shoot 65 in the last round, I wouldn't have thought I'd be able to do that."
Spain's Rafael Cabrera-Bello was the nearest challenger, finishing two shots adrift.
Lewis, from Welwyn Garden City, Hertfordshire, has now jumped 455 places up the world rankings from 621 to 166. He is third in the Ryder Cup race, while the win gurantees him a World Championship debut in Shanghai next month.
Tiger Woods needed five tournaments to land his first professional title. Six-time major winner Sir Nick Faldo, who is also from Welwyn Garden City, took 28, while US Open champion McIlroy did not taste success until his 38th European Tour event.
Lewis two-putted the long 12th and then had four more birdies in a row from the 14th. He kept his nerve to par the dangerous final hole and had to wait the best part of an hour before victory was confirmed.
After his victory, Lewis added: "I played a couple of events in Australia and Dubai earlier this year. I knew the standard was good, but I knew I was able to win.
"It was just whether the nerves and the mind was able to carry on."
Instead of facing a trip to the Tour school in December - he entered the week 234th on the Tour money - he is now exempt for two seasons because of his win.