Swimming at the 2005 World Aquatics Championships – Women's 800 metre freestyle

The Women's 800 Freestyle event at the 11th FINA World Aquatics Championships swam 29 – 30 July 2005 in Montreal, Quebec, Canada. Preliminary heats were held in the Championships morning session on 29 July, with the top-8 finishers advancing to swim-again in the event's Final on 30 July.

At the start of the event, the existing World (WR) and Championships (CR) records were: Note: no new World or Championships records were set during this competition.
 * WR: 8:16.22, Janet Evans (USA), swum 20 August 1989 in Tokyo, Japan
 * CR: 8:23.66, Hannah Stockbauer (Germany), swum 26 July 2003 in Barcelona, Spain