Canada’s Andre de Grasse won his first gold and fifth Olympic medal overall as he overhauled world champion Noah Lyles in the final 50m of the 200m final.
The 26-year-old, who took bronze in the 100m final on Sunday, won in 19.62 seconds, making him the eighth-fastest man in history.
Lyles led into the final quarter but slowed as De Grasse and second-placed Kenny Bednarek ran him down.
Seventeen-year-old Erriyon Knighton finished fourth in 19.93 seconds.
The American teenager broke Rio 2016 champion Usain Bolt’s world junior record for the event in May and may well be its future, but it was De Grasse, himself once the next big thing, who finally lived up to his billing as Bolt’s heir apparent.
De Grasse had set a personal best of 19.73 seconds in Tuesday’s semi-finals and looked relaxed as he strode to the blocks.
In contrast to his smiling and clowning, Lyles struck a serious figure, bellowing into the Tokyo skies as he emerged into the arena.
It was Lyles who led off the bend, but his lead was slowly chewed up as De Grasse and Bednarek – side-by-side in lanes six and seven – came on strong.
De Grasse celebrated with a video call to his partner, American hurdler Nia Ali, at the finish line, seeming to exclaim “finally” during their conversation.
De Grasse has been pegged as a potential successor to Bolt since he finished third behind the Jamaican in the 100m final at the 2015 World Championships aged just 20.
He signed a lucrative deal with the same footwear sponsor as Bolt a few months later. However, hamstring problems stalled his progress before he returned to form with silver and bronze medals at Doha 2019.
“I’ve been waiting for this moment, I’ve been training hard for this moment,” said De Grasse.
“Nineteen point six – I cannot believe the time. And almost 19.5, I’m almost there.”