400 metres hurdles at the Olympics

The 400 metres hurdles at the Summer Olympics is the longest hurdling event held at the multi-sport event. The men's 400 m hurdles has been present on the Olympic athletics programme since 1900, with a sole gap at the 1912 Summer Olympics. The women's event was added to the programme over eighty years later, at the 1984 Olympics. It is the most prestigious 400 m hurdles race at elite level.

The Olympic records for the event are 46.78 seconds for men, set by Kevin Young in 1992, and 52.64 seconds for women, set by Melaine Walker in 2008. Young's time remains the men's world record for the event. That record has been broken at the Olympics on seven occasions: 1908 (the first official IAAF record), 1920, 1932, 1968, 1972, 1976 and 1992. The women's world record has never been broken in Olympic competition.

Edwin Moses is the most successful athlete in the event, having won two gold and one bronze medal. Glenn Davis, Angelo Taylor and Felix Sanchez have also won two Olympic 400 m hurdles titles. Morgan Taylor is the only other athlete beside Moses that has won three medals in the event. Deon Hemmings is the most successful woman, with her 1996 gold and 2000 silver medals, and is the only female athlete to win multiple medals. It is relatively common for 400 m hurdles athletes to also be part of their nation's team for the 4×400 metres relay at the Olympics.

The United States is by far the most successful nation in the men's event with 18 gold medals and 40 medals overall—more than half the medals available. American men have swept the medals on five occasions. The American women have the highest medal total, with seven, but an American woman has never won the event. Russia and Jamaica are the only nations to win multiple women's gold medals, with two each. Great Britain is the only nation to have won a gold medal in both the men's and women's event, having three champions in total.