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

The Men's 400 metre freestyle competition of the 2021 FINA World Swimming Championships (25 m) was held on 16 December 2021.

## Records

Prior to the competition, the existing world and championship records were as follows.
| World record | Yannick Agnel (FRA) | 3:32.25 | Angers, France | 15 November 2012 |
| Competition record | Danas Rapšys (LTU) | 3:34.01 | Hangzhou, China | 11 December 2018 |

## Results
### Heats

The heats were started at 09:30.
| Rank | Heat | Lane | Name | Nationality | Time | Notes |
| 1 | 7 | 5 | Felix Auböck | Austria | 3:37.91 | Q |
| 2 | 5 | 7 | Kieran Smith | United States | 3:38.61 | Q |
| 3 | 7 | 7 | Antonio Djakovic | Switzerland | 3:39.06 | Q, NR |
| 4 | 6 | 5 | Luc Kroon | Netherlands | 3:39.17 | Q |
| 5 | 7 | 2 | Max Litchfield | Great Britain | 3:39.34 | Q |
| 6 | 7 | 4 | Danas Rapšys | Lithuania | 3:39.38 | Q |
| 7 | 4 | 6 | Alfonso Mestre | Venezuela | 3:39.52 | Q, NR |
| 8 | 6 | 3 | Marco De Tullio | Italy | 3:39.53 | Q |
| 9 | 7 | 3 | Matteo Ciampi | Italy | 3:40.10 | |
| 10 | 6 | 0 | Ahmed Hafnaoui | Tunisia | 3:40.30 | |
| 11 | 7 | 6 | Balázs Holló | Hungary | 3:41.75 | |
| 12 | 7 | 8 | Maarten Brzoskowski | Netherlands | 3:41.84 | |
| 13 | 6 | 6 | Henrik Christiansen | Norway | 3:42.03 | |
| 14 | 4 | 3 | Marwan Elkamash | Egypt | 3:42.17 | |
| 15 | 6 | 4 | Tom Dean | Great Britain | 3:42.41 | |
| 16 | 6 | 2 | Daniil Shatalov | Russian Swimming Federation | 3:42.50 | |
| 17 | 5 | 8 | José Paulo Lopes | Portugal | 3:42.57 | NR |
| 18 | 4 | 4 | Denis Loktev | Israel | 3:43.27 | |
| 19 | 5 | 4 | Lee Ho-joon | South Korea | 3:43.35 | |
| 20 | 6 | 7 | Jordan Pothain | France | 3:43.43 | |
| 21 | 7 | 1 | Velimir Stjepanović | Serbia | 3:43.58 | |
| 22 | 5 | 1 | Lukas Märtens | Germany | 3:43.64 | |
| 23 | 4 | 1 | Nguyễn Huy Hoàng | Vietnam | 3:43.89 | NR |
| 24 | 3 | 5 | Juan Morales | Colombia | 3:44.00 | NR |
| 25 | 4 | 5 | Gábor Zombori | Hungary | 3:44.23 | |
| 26 | 5 | 0 | Dimitrios Markos | Greece | 3:44.83 | |
| 27 | 5 | 6 | Aleksandr Egorov | Russian Swimming Federation | 3:44.90 | |
| 28 | 6 | 1 | Stefan Šorak | Serbia | 3:45.01 | |
| 29 | 6 | 8 | Baturalp Ünlü | Turkey | 3:45.66 | |
| 30 | 7 | 9 | Ondřej Gemov | Czech Republic | 3:45.74 | |
| 31 | 5 | 2 | Henning Mühlleitner | Germany | 3:46.05 | |
| 32 | 4 | 7 | David Popovici | Romania | 3:46.08 | |
| 33 | 3 | 2 | Eduardo Cisternas | Chile | 3:46.43 | NR |
| 34 | 4 | 8 | Chen Ende | China | 3:46.61 | |
| 35 | 5 | 3 | Jan Micka | Czech Republic | 3:46.68 | |
| 36 | 4 | 0 | Cheuk Ming Ho | Hong Kong | 3:47.51 | NR |
| 37 | 5 | 5 | Joaquín Vargas | Peru | 3:48.05 | |
| 38 | 4 | 2 | Thomas Thijs | Belgium | 3:48.07 | |
| 39 | 7 | 0 | Yordan Yanchev | Bulgaria | 3:48.12 | |
| 40 | 3 | 4 | Tonnam Kanteemool | Thailand | 3:49.01 | NR |
| 41 | 3 | 6 | Kushagra Rawat | India | 3:49.04 | NR |
| 42 | 3 | 3 | Aflah Prawira | Indonesia | 3:49.13 | NR |
| 43 | 6 | 9 | Mohamed Lagili | Tunisia | 3:50.73 | |
| 44 | 3 | 1 | Mohamed Anisse Djaballah | Algeria | 3:52.01 | |
| 45 | 4 | 9 | Finn McGeever | Ireland | 3:52.34 | |
| 46 | 3 | 7 | Irakli Revishvili | Georgia | 3:53.62 | |
| 47 | 3 | 0 | Adib Khalil | Lebanon | 3:53.64 | NR |
| 48 | 3 | 9 | Omar Abbas | Syria | 3:53.66 | NR |
| 49 | 2 | 3 | Loris Bianchi | San Marino | 3:55.50 | NR |
| 50 | 2 | 4 | Pavel Alovatki | Moldova | 3:55.55 | |
| 51 | 2 | 5 | Joseph Macías | Ecuador | 3:57.51 | |
| 52 | 1 | 3 | Adrián Navarro | Cuba | 3:58.31 | |
| 53 | 3 | 8 | Dylan Cachia | Malta | 3:59.11 | |
| 54 | 2 | 1 | Ado Gargović | Montenegro | 3:59.93 | NR |
| 55 | 2 | 9 | Ramazan Omarov | Kyrgyzstan | 4:02.67 | |
| 56 | 2 | 6 | Nikoli Blackman | Trinidad and Tobago | 4:03.35 | |
| 57 | 2 | 7 | Henrique Mascarenhas | Angola | 4:04.23 | |
| 58 | 2 | 2 | Johan Nónskarð Dam | Faroe Islands | 4:04.95 | |
| 59 | 2 | 0 | Christopher Gossmann | Guatemala | 4:06.06 | |
| 60 | 1 | 5 | Sauod Al-Shamroukh | Kuwait | 4:09.83 | |
| 61 | 2 | 8 | Ahmed Ali Al-Hazmi | Saudi Arabia | 4:12.13 | |
| 62 | 1 | 4 | Ali Imaam | Maldives | 4:24.45 | |
| | 1 | 6 | Mark Imazu | Guam | DSQ | |
| | 1 | 2 | Tesfaye Beyene | Eritrea | DNS | |
| | 5 | 9 | Glen Lim Jun Wei | Singapore | DNS | |

### Final

The final was held at 18:00.
| Rank | Lane | Name | Nationality | Time | Notes |
| | 4 | Felix Auböck | Austria | 3:35.90 | NR |
| | 7 | Danas Rapšys | Lithuania | 3:36.23 | |
| | 3 | Antonio Djakovic | Switzerland | 3:36.83 | NR |
| 4 | 8 | Marco De Tullio | Italy | 3:37.83 | |
| 5 | 5 | Kieran Smith | United States | 3:38.77 | |
| 6 | 6 | Luc Kroon | Netherlands | 3:39.03 | |
| 7 | 1 | Alfonso Mestre | Venezuela | 3:39.06 | NR |
| 8 | 2 | Max Litchfield | Great Britain | 3:39.45 | |