Matthew Centrowitz produced one of the more remarkable performances in United States track and field history on Saturday, becoming the first American to win the 1500 metres since 1908.
The 26-year-old, son of an Olympic middle-distance runner, led every lap and held on at the end to win in three minutes and 50 seconds.
Taoufik Makhloufi (3:50.11) of Algeria got silver and Nicholas Willis (3:50.24) of New Zealand took bronze.
Algeria's Makhloufi had also finished second in the men's 800m earlier in the Games and becomes the first man since Sebastian Coe in 1984 to make the podium in both middle-distance events at the same Olympics.
Any medal would have been redemption for Centrowitz, who finished fourth and four one-hundredths of a second off the podium four years ago in London.
But gold was a shock, as favourite Asbel Kiprop of Kenya ended up sixth and Centrowitz held off Makhloufi.
"My goal was just to get on the podium, I didn't dream of actually winning," Centrowitz told NBC Sports.
He added: "There's nothing like it. It doesn't compare to anything else I've won in my life."
Mel Sheppard was the last American to win the race, at the 1908 London Games. His time was nearly 27 seconds slower than Centrowitz's.
Centrowitz's father, Matt, ran the 1500m at the 1976 Montreal Games.