Athletics at the 1976 Summer Olympics – Women's 400 metres

The Women's 400 metres competition at the 1976 Summer Olympics in Montreal, Quebec, Canada was held at the Olympic Stadium on 25–29 July.

The winning margin was an impressive 1.23 seconds which as of 2023 remains the only time the women's Olympic 400 metres has been won by more than a second.

Competition format
The Women's 400m competition consisted of heats (Round 1), Quarterfinals, Semifinals and a Final. The five fastest competitors from each race in the heats plus the next two fastest overall qualified for the Quarterfinals. The four fastest competitors from each of the Quarterfinal races qualified for the Semifinals, where again the four fastest runners from each heat advanced to the final.

Records
Prior to the competition, the existing World and Olympic records were as follows.

Round 1
Qual. rule: first 5 of each heat (Q) plus the two fastest times (q) qualified.