Tyler Koivisto held on by two strokes to win the Northern Ireland Open supported by the R&A at Galgorm Castle in his first Challenge Tour start.
The American, who only two years ago was teaching fourth-grade in his native Minnesota, shot a three-under 67 in his final round to hold off Norway's Kristian Krogh Johannessen and claim the title at 13-under-par.
With the victory, Koivisto will gain a world ranking spot for the first time in his career and, should other results go his way in events around the world, could be inside the top-500 because of his incredible finish.
Koivisto had taken control of the tournament with an eight-under 62 on Saturday and maintained that stranglehold for the majority of the final round, holding off his rivals until the very end, pipping the late charge of Johannessen to the line.
Having headed into the final round with a three-shot lead over Andrew Wilson (England) and Santiago Tarrio (Spain), Koivisto parred every hole of his front nine as the rest of the field quickly capitalised on his steady start.
In fact, his lead had been cut to one at the turn when Iceland's Gudmundur Kristjansson got to nine-under-par with an eagle at the 10th, but he failed to kick on from there and parred his way in to finish at that mark.
Instead, Koivisto got it going after the ninth, picking up birdies at the first two holes of the back nine to pull back ahead and, despite a bogey at the par-three 14th denting his momentum, he immediately bounced back with a birdie at the 15th.
One by one his rivals also fell away. Wilson had threatened, getting up to 11-under and one back with a birdie at the par-three 12th, but a bogey at the 13th knocked him back and he never recovered. Tarrio, meanwhile, was out of it too after a bogey at the ninth left him too far back.
The only man keeping pace was Johannessen, who cut the lead to one by birdieing the 18th and forcing Koivisto to at least make a par down the last himself to avoid taking it to a play-off.
But the American held his nerve and went one better by birdieing the par-five to secure the championship and an incredible debut success.
The win is made even more remarkable by where Koivisto has come from to reach this stage, the former St Cloud State collegiate golfer deciding to give up his teaching job in 2018 to turn professional.
After earning an invite to the NI Open through Challenge Tour Q-School last year, following a short stint on some minor Tours in the USA, the 27-year-old certainly made the most of his opportunity.
Behind him, Johannessen fired a five-under 65 to take solo second at 11-under, while Sweden's Jens Fahrbring shot the same score in a bogey-free fourth round to finish in a tie for fourth with Wilson at 10-under.
The best local finisher was John Ross Galbraith (Whitehead), who managed to net himself a tie for 19th after a 70 in his final round, which saw him finish at four-under-par overall.
Irish duo Niall Kearney (-2) and Conor O'Rourke (+17) were the other two local players to make the halfway cut.
Attentions at Galgorm Castle will now turn to two weeks' time when the Dubai Duty Free comes to the Co Antrim course, with the European Tour's top starts set to do battle at what should be a fantastic venue.