The Men's 50 Butterfly event at the 11th FINA World Aquatics Championships swam 26–-27 July 2005 in Montreal, Canada.

Preliminary[1] and Semifinal[2] heats swam on 26 July, with the Final[3] on 27 July.

Prior to the competition, the existing World (WR) and Championship (CR) records were: Swim-off for 16th Results from the swim-off for 16th place, between Milorad Cavic and Kaio Almeida were: