It took a dramatic dive by Shaunae Miller of Bahamas at the finish line to win the women's 400-metre final, preventing American Allyson Felix from capturing a record fifth Olympic gold medal.
Miller clocked 49.44 seconds, running in lane 7, to narrowly hold off Felix, who finished in 49.51.
Shericka Jackson of Jamaica won the bronze in 49.85.
Felix won the 400 at the world championships last year and was planning to run the 200- and 400-metre double in Rio, but was hampered by an ankle injury at the U.S. trials and didn't make the team for the 200.
She won the 200 in London four years ago.
Felix now has seven Olympic medals, including three silvers.
She could still run both the 4x100 and the 4x400 relays in Rio.The 30-year-old American entered the games as one of six women with four Olympic gold medals in track and field.