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.

Heats
The heats were started at 09:30.

Final
The final was held at 18:00.