The final of the women's 400 metre individual medley event at the 1984 Summer Olympics was held in the McDonald's Olympic Swim Stadium in Los Angeles, California, on July 29, 1984.

[1] 20 athletes competed in the heats, with the eight fastest qualifying for the final.

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

Rule: The eight fastest swimmers advance to final A (Q), while the next eight to final B (q).

[2]