After two false starts by other skaters, Ohno anticipated the gun perfectly and broke away from the line clear of the other four finalists. He led the entire way and didn't have to worry about Ahn, who got caught up behind two Canadians, Francois-Louis Tremblay and Eric Bedard.
Ohno looked back once, threw up his arms and let out a scream when he crossed the line first. He jumped into the arms of a U.S. coach and grabbed an American flag for the victory lap.
Showing there were no hard feelings from Salt Lake City, Ahn came over to shake Ohno's hand in the middle of the rink.
Tremblay held on for second while Ahn passed Bedard to claim the bronze. The South Korean became the first skater to win three individual medals in short track, but he fell short of three golds after winning the 1,000 and 1,500.
As for Ohno, he grabbed the fourth Olympic medal of his career. He was one of the most feted athletes at the Salt Lake City Games, where he won a gold and a silver in thrilling races.
At Turin, Ohno failed to qualify for the final of the 1,500 and settled for bronze in the 1,000, falling into the category of high-profile Americans who appeared to be falling short of expectations.
Ohno had a chance to win a second gold medal later Saturday in the 5,000 relay.
Four years ago, the soul-patched American picked up his medals in two wacky races. There was a disputed gold in the 1,500, when a South Korean was disqualified for an illegal block on Ohno.
Ohno got silver in the 1,000 when the top four skaters wiped out on the final turn, but he still managed to crawl across the line in second, then went to the medal ceremony in a wheelchair.
There was nothing controversial about this gold - at least in the final.
Ohno did get some help from the judges earlier in the night. He appeared to finish third in the semifinals - which wouldn't have been good enough to advance. But he moved on when China's Li Jiajun, a veteran of four Olympics, was disqualified for impeding another skater.
In other Olympics news:
The American skier ended his disappointing Olympics Saturday by failing to complete yet another run, this time in the men's slalom, the final Alpine event of the Turin Games.
Miller had failed to finish 11 of 14 slaloms since December 2004, so it was no shock when he straddled a gate and skied off the course after only 15 seconds. He failed to medal in Turin despite skiing all five Alpine events.
Miller, who has been a local nightlife fixture throughout the games, told The Associated Press he was content with his experience.
"As far as my own personal involvement, I would not change anything. I had an awesome Olympics," Miller said. "My preparation certainly could have been different, but I'm not a guy who looks back."