| Event: | Men's 800m Freestyle |
| Competition: | 2003 FINA World Aquatics Championships |
| Dates: | 24 July (prelims) 25 July (final) |
| Win Value: | 7 minute 43.82 seconds |
| Gold: | Grant Hackett |
| Goldnoc: | AUS |
| Silver: | Larsen Jensen |
| Silvernoc: | USA |
| Bronze: | Ihor Chervynskyi |
| Bronzenoc: | UKR |
| Prev: | 2001 |
| Next: | 2005 |
See main article: Swimming at the 2003 World Aquatics Championships.
The Men's 800 Freestyle event at the 10th FINA World Aquatics Championships swam on July 24–25, 2003 in Barcelona, Spain. Preliminary heats of the event were swum during the morning session on July 24,[1] with the Final being held during the evening session on July 25.[2]
Prior to the start of the event, the existing World (WR) and Championship (CR) records were both:
| Place | Swimmer | Nation | Time | Notes |
|---|---|---|---|---|
| 1 | 7:43.82 | |||
| 2 | 7:48.09 | NR | ||
| 3 | 7:53.15 | |||
| 4 | 7:53.48 | |||
| 5 | 7:57.22 | |||
| 6 | 8:01.75 | |||
| 7 | 8:02.38 | |||
| 8 | 8:04.10 | |||
| Rank | Heat+Lane | Swimmer | Nation | Time | Notes | |
|---|---|---|---|---|---|---|
| 1 | H4 L4 | Grant Hackett | 7:55.15 | q | ||
| 2 | H2 L4 | Graeme Smith | 7:58.66 | q | ||
| 3 | H3 L4 | Larsen Jensen | 7:59.18 | q | ||
| 4 | H4 L3 | Kurtis MacGillivary | 7:59.58 | q | ||
| 5 | H2 L3 | Dragoș Coman | 8:00.44 | q | ||
| 6 | H3 L2 | Ihor Chervynskyi | 8:00.61 | q | ||
| 7 | H2 L2 | Shunichi Fujita | 8:02.84 | q | ||
| 8 | H3 L1 | Lin Zhang | 8:04.74 | q | ||
| 9 | H3 L5 | Stephen Penfold | 8:06.48 | |||
| 10 | H3 L7 | Shilo Ayalon | 8:07.85 | |||
| 11 | H2 L1 | Hannes Kalteis | 8:08.17 | |||
| 12 | H4 L7 | Chad Carvin | 8:08.48 | |||
| 13 | H2 L6 | Dimitros Manganas | 8:10.07 | |||
| 14 | H2 L7 | Felipe Araujo | 8:10.56 | |||
| 15 | H3 L6 | Kyu Chul Han | 8:13.47 | |||
| 16 | H4 L8 | Gian Carlo Zolezzi | 8:14.62 | |||
| 17 | H4 L1 | Luiz Lima | 8:15.08 | |||
| 18 | H4 L2 | Cheng Yu | 8:16.23 | |||
| 19 | H3 L3 | Rick Say | 8:17.31 | |||
| 20 | H3 L8 | Yi-Khy Saw | 8:22.99 | |||
| 21 | H2 L8 | Shai Livant | 8:24.14 | |||
| 22 | H1 L4 | Mohammad Naeem Masri | 8:30.00 | |||
| 23 | H1 L3 | Kwok Leung Chung | 8:31.10 | |||
| 24 | H1 L5 | Roberto Peñailillo | 8:34.10 | |||
| 25 | H1 L6 | Neils Agius | 9:09.73 | |||
| 26 | H1 L2 | Steven Mangroo | 9:16.60 | |||
| 27 | H1 L7 | Barnsley Albert | 9:27.30 | |||
| - | - | David Davies | DNS | |||
| - | - | Emiliano Brembilla | DNS | |||
| - | - | Trevor Kakunze | DNS | |||