A sensational run of 9.79 from Lamont Marcell Jacobs saw him become the first Italian to ever win the men's 100m and the most unlikely of successors to Usain Bolt as the sprint king of the Olympics.
In the end he came home with time to spare in a blistering run of 9.80 seconds that is a personal and European best and came moments after compatriot Gianmarco Tamberi won gold in the high jump.
American Fred Kerley picked up the silver medal and Canadian Andre De Grasse took bronze.
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It is the first time since the 2000 Olympics that the legendary Bolt has not been competing and few saw Jacobs as the man to inherit his title.
It led to one the most open fields in recent history and there were shocks before the final with pre-games favourite Trayvon Bromell looking out of sorts and failing to qualify.
Great Britain's Zharnel Hughes was disqualified for a false start.
'It's really, really, really amazing!' - Jacobs reacts to 'dream' 100m gold
Kerley (9.84) was the fastest athlete over the first 50 metres after a superb start from the former 400m runner.
However the powerful Jacobs gathered speed as he moved into his stride, legs pumping to move past Kerley, who also set a personal best, as the line neared.
Andre de Grasse came through to take third, completing a podium of personal bests with a time of 9.89 ahead of Akani Simbine of South Africa.
Gianmarco Tamberi e Marcell Jacobs - Tokyo 2020
Image credit: Getty Images
There was disappointment for Hughes, who revealed a cramp in his leg caused a twitch and his disqualification, and for Nigeria's Enoch Adegoke, who appeared to be in the medal mix before pulling up with an injury with about 30 metres to run.
Jacobs was born in El Paso, Texas but grew up on the shores of Lake Garda, and is a former Italian long jump champion.
He dipped under ten seconds in the 100m for the first time in May and twice set lifetime bests at these Olympics.
After victory, Jacobs was embraced by compatriot Tamberi to celebrate double triumph for Italy, continuing a golden sporting summer for the country.
Hughes, meanwhile, revealed to Eurosport and discovery+ expert Greg Rutherford that his false start was caused by a cramp in his lower leg.
"It wasn’t pressure," explained Hughes. "I wasn’t nervous. It’s just that my calf cramped up when I went up on ‘set’, and with the cramp I moved, which is heart-breaking. I’m really gutted right now. I worked too hard to be here to come and false start. It hurts a lot. I just have to gather my thoughts together now and try to re-focus for the 4 x 100m.
"Before I got here I was suffering with a Psoas problem and the fact that I showed up and made it to the finals, I want to give credit to my team back there.
"I’m sorry this had to happen like this, it’s just unfortunate like I said that the calf cramped and I moved. I’m sorry."
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