Swimming at the 2020 Summer Olympics – Men's 100 metre backstroke

The men's 100 metre backstroke event at the 2020 Summer Olympics was held from 25 to 27 July 2021 at the Tokyo Aquatics Centre. It was the event's twenty-sixth appearance, having been held at every edition since 1904 except 1964. Moreover, these Games marked the first time when the men's sprint backstroke event was held in Tokyo, as the event was not included in the swimming program in 1964.

The event has been historically dominated by Americans, having won 15 gold medals in the event's 25 past appearances including six-straight titles since 1996.

Summary
Breaking a long run of American dominance in this event, the ROC's defending bronze medallist Evgeny Rylov (51.98) edged his compatriot Kliment Kolesnikov to claim the Committee's first gold in this event and its first in swimming since Larisa Ilchenko won the Women's marathon 10 kilometre in 2008. Leading at the turn by 6 one-hundredths of a second over Rylov, Kolesnikov could not maintain his lead and settled for silver just 0.02 seconds behind in 52.00. The ROC's quinella also denied the U.S. a gold or silver for the first time in this event since 1980 as despite a late charge, the U.S.' defending champion Ryan Murphy could not overtake the ROC duo, settling for bronze in 52.19.

Italy's Thomas Ceccon clocked a national record of 52.30 to fall short of the podium, placing fourth. Meanwhile China's two-time defending World champion Xu Jiayu (52.51) fell to fifth, while Spain's Hugo González (52.78) edged Australia's Mitch Larkin (52.79) by one one-hundredth of a second to take sixth. Romania's Robert Glință (52.95) clocked a sub-53 time to round out the field.

Records
Prior to this competition, the existing world and Olympic records were as follows.

No new records were set during the competition.

Qualification
The Olympic Qualifying Time for the event was 53.85 seconds. Up to two swimmers per National Olympic Committee (NOC) could automatically qualify by swimming that time at an approved qualification event. The Olympic Selection Time was 55.47 seconds. Up to one swimmer per NOC meeting that time was eligible for selection, allocated by world ranking until the maximum quota for all swimming events is reached. NOCs without a male swimmer qualified in any event could also use their universality place.

Competition format
The competition consisted of three rounds: heats, semifinals, and a final. The swimmers with the best 16 times in the heats advanced to the semifinals. The swimmers with the best 8 times in the semifinals advanced to the final.

Schedule
All times are Japan Standard Time (UTC+9)

Heats
The swimmers with the top 16 times, regardless of heat, advanced to the semifinals.

Semifinals
The swimmers with the best 8 times, regardless of heat, advanced to the final.