The women's 100 metre freestyle event at the 2020 Summer Olympics was held from 28 to 30 July 2021 at the Tokyo Aquatics Centre.

Though first at the 50, Hong Kong's Siobhan Haughey was overtaken by McKeon down the stretch but still won her second silver medal at these Games with an Asian record of 52.27.

Femke Heemskerk (52.79) clocked a new Dutch record to come sixth while Great Britain's Anna Hopkin (52.83) and the U.S.'s Abbey Weitzeil (53.23) rounded out the finalists.

Up to two swimmers per National Olympic Committee (NOC) can automatically qualify by swimming that time at an approved qualification event.

Up to one swimmer per NOC meeting that time is eligible for selection, allocated by world ranking until the maximum quota for all swimming events is reached.