The Men's 100 metre butterfly competition of the swimming events at the 2015 World Aquatics Championships was held on 7 August with the heats and the semifinals and 8 August with the final.

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

The heats were held at 10:09[2] The semifinals were held on 7 August at 18.35.

[3] The final was held on 8 August at 18:13.

[4]