Swimming at the 2016 Summer Olympics – Women's 100 metre freestyle

The women's 100 metre freestyle event at the 2016 Summer Olympics took place between 10–11 August at the Olympic Aquatics Stadium.

In one of the most unexpected results at these Games, Canadian teenager Penny Oleksiak and U.S. sprinter Simone Manuel pulled off an enormous upset from Australia's pre-race favorites Bronte and Cate Campbell down the home stretch to share their historic Olympic gold-medal triumph in this event. About midway of the final lap, both Oleksiak and Manuel came from behind to overhaul almost the entire field, before touching the wall simultaneously for an Olympic record in 52.70. Building a new milestone, Manuel became the first ever African-American female to earn an Olympic gold, while Oleksiak picked up her fourth medal to establish herself as Canada's most successful athlete at a single edition in Summer Olympic history.

Sweden's Sarah Sjöström captured the bronze with a 52.99 to complete a full set of medals that she already collected at the Games, edging out Bronte Campbell (53.04) to fourth by a 0.05-second deficit. Dutch sprinter Ranomi Kromowidjojo missed her chance to defend the title with a fifth-place time in 53.08, while world-record holder Cate Campbell, who broke the existing Olympic record twice each in both the heats and semifinals earlier, slipped to sixth in 53.24. Manuel's teammate Abbey Weitzeil (53.30) and Denmark's four-time Olympian Jeanette Ottesen (53.36) rounded out a historic top eight.

Notable swimmers missed the final roster, including Brazil's home-crowd favorite Etiene Medeiros, Belarus' two-time Olympic medalist Aliaksandra Herasimenia, and Italy's Federica Pellegrini, who scratched the afternoon prelims earlier to focus on her 4×200 m freestyle relay duty instead.