Lamont Marcell Jacobs has become one of the biggest surprise winners - and the first Italian champion - in the history of Olympic men's 100 metres.
Jacobs smashed his personal best and set a new European record in the title race on Saturday night with a winning time of 9.80 seconds.
American Fred Kerley claimed the silver medal in 9.84 and Canada's Andre de Grasse took the bronze in 9.89, with all three medallists setting PBs.
It was the first Olympic 100m final of the post-Usain Bolt era - and not a single Jamaican qualified for the medal race.
The now-retired Bolt had won the previous three Olympic 100m crowns but instead of a marquee global name, many were left asking 'Lamont who?' after the US-born Jacobs raced to the title.
Nobody was more amazed than the winner. "I don't know, it's a dream, a dream, it is fantastic. Maybe tomorrow I can imagine what they are saying, but today it is incredible," said Jacobs.
"It's been my dream since I was a child. I need a week or so to understand what has happened.
"I've won an Olympic gold after Bolt, it's unbelievable. Tonight, staring at the ceiling, perhaps I will realize."
Even in a race with no clear favourites, the 26-year-old Jacobs proved a surprise champion - and his victory came on quite a night for Italy, just a few minutes after countryman Gianmarco Tamberi had tied Qatari high jumper Mutaz Essa Barshim for gold.
Jacobs was born in El Paso, Texas - the son of an American father and an Italian mother and moved to Italy as a young boy when the US military transferred his dad to South Korea.
He was a long jump specialist for years, and his biggest major success was an indoor 60 metres win at the European Indoor championships.
His path was made easier when American Trayvon Bromell, who came into Tokyo with the world's leading time and as the odds-on favourite, didn't even make the final, finishing third in his semi.
Australian Rohan Browning was also run out in the semis after finishing fifth in 10.09 - eight hundredths of a second slower than he clocked in the opening round on Saturday.
Australian Associated Press