| Event: | Men's 800m Freestyle |
| Competition: | 2005 FINA World Aquatics Championships |
| Dates: | 26 July (prelims) 27 July (final) |
| Competitors: | 45 |
| Win Value: | 7:38.65 |
| Gold: | Grant Hackett |
| Goldnoc: | AUS |
| Silver: | Larsen Jensen |
| Silvernoc: | USA |
| Bronze: | Yuri Prilukov |
| Bronzenoc: | RUS |
| Prev: | 2003 |
| Next: | 2007 |
See main article: Swimming at the 2005 World Aquatics Championships.
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.
| World record | 7:39.16 | Fukuoka, Japan | align=right | 24 July 2001 | ||
| Championship record | 7:39.16 | Fukuoka, Japan | align=right | 24 July 2001 |
The following records were established during the competition:
| Place | Name | Nationality | Time | Note |
|---|---|---|---|---|
| 1 | 7:38.65 | |||
| 2 | 7:45.63 | AM | ||
| 3 | 7:46.64 | ER | ||
| 4 | 7:50.83 | |||
| 5 | 7:51.03 | |||
| 6 | 7:51.54 | |||
| 7 | 7:58.62 | |||
| 8 | 8:03.52 | |||
| Rank | Name | Nationality | Time | Note |
|---|---|---|---|---|
| 1 | 7:47.63 | Q | ||
| 2 | 7:48.89 | Q | ||
| 3 | 7:51.75 | Q | ||
| 4 | 7:51.92 | Q | ||
| 5 | 7:52.04 | Q | ||
| 6 | 7:52.55 | Q | ||
| 7 | 7:52.56 | Q | ||
| 8 | 7:53.33 | Q | ||
| 9 | 7:54.55 | |||
| 10 | 7:56.38 | |||
| 11 | 7:57.11 | |||
| 12 | 7:57.79 | |||
| 13 | 7:58.00 | |||
| 14 | 7:59.09 | |||
| 15 | 7:59.60 | |||
| 16 | 7:59.65 | |||
| 17 | 7:59.66 | |||
| 18 | 7:59.69 | |||
| 19 | 8:00.06 | |||
| 20 | 8:04.67 | |||
| 21 | 8:05.65 | |||
| 22 | 8:06.98 | |||
| 23 | 8:07.46 | |||
| 24 | 8:08.52 | |||
| 25 | 8:08.66 | |||
| 26 | 8:09.01 | |||
| 27 | 8:09.23 | |||
| 28 | 8:09.32 | |||
| 29 | 8:12.91 | |||
| 30 | 8:16.93 | |||
| 31 | 8:18.06 | |||
| 32 | 8:20.55 | NR | ||
| 33 | 8:23.13 | |||
| 34 | 8:28.73 | |||
| 35 | 8:29.83 | |||
| 36 | 8:29.91 | |||
| 37 | 8:39.94 | |||
| 38 | 8:41.81 | |||
| 39 | 8:48.71 | |||
| 40 | 8:53.14 | |||
| 41 | 8:54.73 | |||
| 42 | 8:55.03 | NR | ||
| 43 | 8:58.55 | |||
| 44 | 9:17.94 | |||
| -- | DNS | |||