Simone Manuel of the United States and 16-year-old Penny Oleksiak of Canada tied for the gold medal in the women's 100-meter freestyle, upsetting world-record holder Cate Campbell.
Manuel becomes the first African-American woman to win an Olympic gold medal in swimming.
Campbell was on pace to take her world record even lower when she made the turn out front, with little sister Bronte right behind her. But the Australian siblings, who teamed up to lead their country to gold in the 4x100 freestyle relay, couldn't hang on.
Bronte faded to fourth, and Cate dropped all the way to sixth at the finish.
Instead, it was Manuel -- her fingernails painted red, white and blue -- who touched at the same time as Oleksiak, the youngest swimmer in the field.
Manuel broke down in tears when she recognized her historic achievement in a sport that still has few African-Americans.