The Women's 400 Freestyle at the 11th FINA World Aquatics Championships was swum on 24 July 2005 in Montreal, Quebec, Canada. Preliminary heats were swum that morning, with the top-8 finishers advancing to swim the race again in that evenings Final. As the competition was held in a long course (50m) pool, the race consisted of 8 lengths of freestyle. At the start of the event, the existing World (WR) and Championships (CR) records were: