100 metres, Men

The three-time defending champion, Usain Bolt, was no longer competing and this was the first Olympic sprints competition without him since the 2000 Sydney Olympics. In his absence there was no clear favorite. The best sprinter since Rio had been American Christian Coleman, who won the 2019 World Championship, but he fell afoul of whereabouts failures and was subject to a doping penalty, which kept him out of Tokyo.

The slight favorite for this event, per Track & Field News, was American Trayvon Bromell, who was coming back from injuries and had won the US Olympic Trials. Also considered were another USA sprinter, Ronnie Baker, runner-up to Bromell at the Trials, and Canadian Andre De Grasse, also returning from sub-par years, but De Grasse had won bronze in this event at Rio, along with a silver in the 200.

Bromell did not produce at Tokyo, and failed to make the final. Baker and De Grasse qualified, with Baker considered a slight favorite. Baker led the final through the first 50 metres, but at that point was caught by the American-born Italian Lamont Marcell Jacobs. Jacobs moved ahead, pushed by another US runner, Fred Kerley who, until 2021, had been primarily a 400 metre specialist.

De Grasse had started poorly out in lane 9, but started closing, but Jacobs could not be headed, and the Italian took the gold medal over Kerley, with De Grasse repeating his bronze medal from Rio, as Baker fell back to fifth place.

Jacobs was not a complete unknown as some in the media made him out to be, as TAFNews ranked him fifth in their pre-Olympic predictions but the victory was still an upset. Jacobs was born of an Italian-mother and an American soldier, and was raised initially in Texas, but when his father was re-assigned to Korea, Lamont and his mother returned to Italy and he rarely saw his father again.