Swimming at the 2019 World Aquatics Championships – Women's 400 metre freestyle

The women's 400-metre freestyle competition at the 2019 World Championships was held on 21 July 2019. Ariarne Titmus overcame a .62-second deficit in the last 50 metres to defeat defending champion Katie Ledecky. This was Ledecky's first loss in a major international 400 metre freestyle competition.

Records
Prior to the competition, the existing world and championship records were as follows.

Heats
The heats were held at 11:22.

Final
The final was held at 20:33.