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

The women'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-third consecutive appearance, having been held at every edition since 1924. An unusual occurrence happened where the Olympic record for this event was broken three times in a single day and five times through the course of the entire competition.

Summary
Australia's world record holder Kaylee McKeown broke the Olympic record to win her first individual Olympic title in 57.47, just 0.02 seconds off her world record. Third at the turn, McKeown used a blistering back half to overtake the field and become Australia's first Olympic champion in this event. While Canada's defending Bronze medallist Kylie Masse led at the halfway mark, she could not withstand McKeown's late charge, touching for silver in 57.72 - only 0.02 seconds off her national record. U.S.' previous world record holder Regan Smith was unable to replicate her time from the heats and semi-finals, settling for bronze in 58.05. Though Smith's teammate Rhyan White (58.43) was second at the turn, she would fade over the final 50 m to take fourth place. Australia's Emily Seebohm (58.45), the 2012 silver medallist, was out-touched by 0.02 seconds to finish fifth.

Meanwhile Great Britain's Kathleen Dawson could not repeat her stunning 58.01 swim from the European Championships months earlier, placing sixth. Dutch record holder Kira Toussaint also missed her national record from the Eindhoven Qualification Meet to take sixth. Israel's Anastasia Gorbenko came eight in 59.90, missing her personal best time from the semi-finals by 6 tenths of a second.

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

The following records were established during the competition:

Qualification
The Olympic Qualifying Time for the event was 1:00.25. 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 1:02.06. 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 female 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.