The Men's 50 metre butterfly competition of the 2018 FINA World Swimming Championships (25 m) was held on 14 and 15 December 2018 at the Hangzhou Olympic Sports Center.

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

The following new records were set during this competition: The heats were started at 9:52.

[2] The swim-off was held on 14 December at 11:07.

[3] The semifinals were held at 19:33.