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

The Men's 800m Freestyle at the 11th FINA World Aquatics Championships occurred on the morning of 26 July 2005 (preliminary heats) and in the evening of 27 July 2005 (final heat) in the Olympic pool at Parc Jean-Drapeau in Montreal, Canada. 45 swimmers were entered in the event, of which 44 swam. The top-8 swimmers from the morning heats advanced to the next day's final heat.

Records
The following records were established during the competition: