Swimming at the 2001 World Aquatics Championships – Men's 100 metre butterfly

The men's 100 metre butterfly event at the 2001 World Aquatics Championships took place 26 July. The heats and semifinals took place on 25 July, with the final being held on 26 July.

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

The following record was established during the competition: