2021 FINA World Swimming Championships (25 m) – Men's 400 metre individual medley
# 2021 FINA World Swimming Championships (25 m) – Men's 400 metre individual medley

The Men's 400 metre individual medley competition of the 2021 FINA World Swimming Championships (25 m) was held on 20 December 2021.

## Records

Prior to the competition, the existing world and championship records were as follows.

| World record | Daiya Seto (JPN) | 3:54.81 | Las Vegas, United States | 20 December 2019 |
| - | - | - | - | - |
| Competition record | Ryan Lochte (USA) | 3:55.50 | Dubai, United Arab Emirates | 16 December 2010 |

## Results

### Heats

The heats were started at 09:53.

| Rank | Heat | Lane | Name | Nationality | Time | Notes |
| - | - | - | - | - | - | - |
| 1 | 3 | 4 | Daiya Seto | Japan | 4:00.84 | Q |
| 2 | 3 | 1 | Carson Foster | United States | 4:02.63 | Q |
| 3 | 2 | 4 | Ilya Borodin | Russian Swimming Federation | 4:04.35 | Q |
| 4 | 2 | 2 | Balázs Holló | Hungary | 4:04.74 | Q |
| 5 | 2 | 0 | Kieran Smith | United States | 4:04.82 | Q |
| 6 | 2 | 5 | Alberto Razzetti | Italy | 4:05.05 | Q |
| 7 | 3 | 0 | Eitan Ben Shitrit | Israel | 4:07.55 | Q |
| 8 | 2 | 6 | Brandonn Almeida | Brazil | 4:08.29 | Q |
| 9 | 3 | 6 | Andreas Vazaios | Greece | 4:09.53 | |
| 10 | 3 | 8 | Héctor Ruvalcaba | Mexico | 4:10.83 | NR |
| 11 | 3 | 2 | Daniil Pasynkov | Russian Swimming Federation | 4:11.74 | |
| 12 | 1 | 4 | Miguel Cancel | Puerto Rico | 4:13.12 | |
| 13 | 1 | 5 | Aflah Fadlan Prawira | Indonesia | 4:13.61 | NR |
| 14 | 3 | 9 | Erick Gordillo | Guatemala | 4:14.58 | NR |
| 15 | 1 | 3 | Nguyễn Hữu Kim Sơn | Vietnam | 4:15.71 | |
| 16 | 3 | 7 | Leonardo Coelho Santos | Brazil | 4:19.16 | |
| 17 | 1 | 6 | Simon Bachmann | Seychelles | 4:30.97 | |
| 18 | 1 | 7 | Rashad Alguliyev | Azerbaijan | 4:32.30 | |
| | 1 | 2 | Brandon Schuster | Samoa | DNS | |
| | 2 | 1 | Wang Shun | China | DNS | |
| | 2 | 3 | Tomoe Hvas | Norway | DNS | |
| | 2 | 7 | José Paulo Lopes | Portugal | DNS | |
| | 2 | 8 | Richard Nagy | Slovakia | DNS | |
| | 2 | 9 | Jaouad Syoud | Algeria | DNS | |
| | 3 | 3 | Max Litchfield | Great Britain | DNS | |
| | 3 | 5 | Duncan Scott | Great Britain | DNS | |

### Final

The final was held at 19:25.

| Rank | Lane | Name | Nationality | Time | Notes |
| - | - | - | - | - | - |
| | 4 | Daiya Seto | Japan | 3:56.26 | |
| | 3 | Ilya Borodin | Russian Swimming Federation | 3:56.47 | ER, WJ |
| | 5 | Carson Foster | United States | 3:57.99 | |
| 4 | 7 | Alberto Razzetti | Italy | 3:59.57 | NR |
| 5 | 2 | Kieran Smith | United States | 4:03.29 | |
| 6 | 1 | Eitan Ben Shitrit | Israel | 4:08.31 | |
| 7 | 8 | Brandonn Almeida | Brazil | 4:08.77 | |
| 8 | 6 | Balázs Holló | Hungary | 4:11.26 | |
