The 400 metres at the Summer Olympics has been contested since the first edition of the multi-sport event. The men's 400 m has been present on the Olympic athletics programme since 1896 but nearly seventy years passed before the introduction of the women's 400 m, which has been held continuously since the 1964 Games. It is the most prestigious 400 m race at elite level. The competition format typically has two qualifying rounds leading to a final race between eight athletes.

The 4 × 400 metres relay at the Summer Olympics is the longest track relay event held at the multi-sport event. The men's relay has been present on the Olympic athletics programme since 1912 and the women's event has been continuously held since the 1972 Olympics. The inaugural and so far the only mixed 4 × 400 metres relay was held at the 2020 Olympics. It is the most prestigious 4×400 m relay race at elite level. At the 1908 Summer Olympics, a precursor to this event was held – the 1600 m medley relay. This event, with two legs of 200 m, one of 400 m, and a final leg of 800 m, was the first track relay in Olympic history.