2021 FINA World Swimming Championships (25 m) – Men's 100 metre butterfly

The Men's 100 metre butterfly competition of the 2021 FINA World Swimming Championships (25 m) was held on 17 and 18 December 2021.

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

Heats
The heats were started on 17 December at 10:23.

Semifinals
The semifinals were started on 17 December at 19:26.

Final
The final was held on 18 December at 18:07.