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.

[1] 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.

The Women's 400m competition consisted of heats (Round 1), quarterfinals, semifinals and a final.

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

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