| Event: | Men's 400m Individual Medley |
| Competition: | 2003 FINA World Aquatics Championships |
| Dates: | 27 July |
| Win Value: | 4 minute 09.09 seconds |
| Gold: | Michael Phelps |
| Goldnoc: | USA |
| Silver: | László Cseh |
| Silvernoc: | HUN |
| Bronze: | Oussama Mellouli |
| Bronzenoc: | TUN |
| Prev: | 2001 |
| Next: | 2005 |
See main article: Swimming at the 2003 World Aquatics Championships.
The Men's 400 Individual Medley event at the 10th FINA World Aquatics Championships swam on July 27, 2003 in Barcelona, Spain. Preliminary heats[1] swam during the morning session, with the top-8 finisher advancing to swim again in the Final[2] that evening.
At the start of the event, the existing World (WR) and Championship (CR) records were both:
| Rank | Swimmer | Nation | Time | Notes |
|---|---|---|---|---|
| 1 | 4:09.09 | WR | ||
| 2 | 4:10.79 | |||
| 3 | 4:15.36 | |||
| 4 | 4:16.06 | |||
| 5 | 4:17.30 | |||
| 6 | 4:17.54 | |||
| 7 | 4:20.27 | |||
| 8 | 4:21.23 | |||
| Rank | Heat/Lane | Swimmer | Nation | Time | Notes |
|---|---|---|---|---|---|
| 1 | H6 L5 | 4:14.11 | q | ||
| 2 | H7 L4 | 4:15.72 | q | ||
| 3 | H5 L4 | 4:17.12 | q | ||
| 4 | H7 L3 | 4:17.21 | q | ||
| 5 | H5 L3 | 4:18.21 | q | ||
| 6 | H5 L5 | 4:18.33 | q | ||
| 7 | H6 L4 | 4:18.88 | q | ||
| 8 | H6 L6 | 4:19.50 | q | ||
| 9 | H5 L8 | 4:19.72 | |||
| 10 | H6 L2 | 4:20.10 | |||
| 11 | H6 L3 | 4:20.51 | |||
| 11 | H6 L1 | 4:20.51 | |||
| 13 | H7 L2 | 4:20.52 | |||
| 14 | H7 L1 | 4:20.61 | |||
| 15 | H7 L6 | 4:20.67 | |||
| 16 | H7 L5 | 4:20.92 | |||
| 17 | H4 L5 | 4:21.23 | |||
| 18 | H5 L6 | 4:21.74 | |||
| 19 | H5 L1 | 4:21.76 | |||
| 20 | H7 L8 | 4:22.34 | |||
| 21 | H6 L8 | 4:23.16 | |||
| 22 | H5 L2 | 4:23.29 | |||
| 23 | H4 L7 | 4:25.14 | |||
| 24 | H4 L3 | 4:25.32 | |||
| 25 | H4 L4 | 4:26.07 | |||
| 26 | H6 L7 | 4:26.27 | |||
| 27 | H5 L7 | 4:27.69 | |||
| 28 | H4 L8 | 4:27.80 | |||
| 29 | H3 L4 | 4:27.94 | |||
| 30 | H4 L1 | 4:28.27 | |||
| 31 | H3 L6 | 4:28.37 | |||
| 32 | H3 L5 | 4:29.17 | |||
| 33 | H3 L2 | 4:30.19 | |||
| 34 | H3 L3 | 4:32.27 | |||
| 35 | H2 L4 | 4:33.26 | |||
| 36 | H4 L6 | 4:33.52 | |||
| 37 | H3 L8 | 4:37.21 | |||
| 38 | H4 L2 | 4:37.90 | |||
| 39 | H3 L7 | 4:38.13 | |||
| 40 | H2 L2 | 4:41.41 | |||
| 41 | H2 L7 | 4:41.49 | |||
| 42 | H2 L5 | 4:41.55 | |||
| 43 | H1 L4 | 4:44.13 | |||
| 44 | H2 L3 | 4:46.30 | |||
| 45 | H2 L6 | 4:48.33 | |||
| 46 | H1 L5 | 4:55.06 | |||
| 47 | H1 L2 | 4:56.15 | |||
| 48 | H2 L1 | 4:57.90 | |||
| 49 | H1 L3 | 5:01.16 | |||
| 49 | H1 L1 | 5:01.16 | |||
| 51 | H1 L7 | 5:10.29 | |||
| - | H7 L7 | DQ | |||
| - | - | DNS | |||
| - | - | DNS | |||
| - | - | DNS | |||
| - | - | DNS | |||