The final of the women's 400 metre freestyle event at the 1984 Summer Olympics was held in the McDonald's Olympic Swim Stadium in Los Angeles, California, on July 31, 1984.

[1] Prior to this competition, the existing world and Olympic records were as follows.

The following records were established during the competition: Rule: The eight fastest swimmers advance to final A (Q), while the next eight to final B (q).

[2]