The Men's 100 metre freestyle competition of the 2021 FINA World Swimming Championships (25 m) was held on 20 and 21 December 2021.

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

The heats were started on 20 December at 10:26.

[2] The semifinals were started on 20 December at 18:14.

[3] The final was held on 21 December at 18:35.