Swimming at the 2005 World Aquatics Championships – Women's 100 metre butterfly

The Women's 100 Butterfly event at the 11th FINA World Aquatics Championships swam on 24–25 July 2005 in Montreal, Canada. Preliminary and Semifinal heats swam on 24 July. The Final swam in the evening session of 25 July.

At the start of the event, the existing World (WR) and Championships (CR) records were:
 * WR: 56.61 swum by Inge de Bruijn (Netherlands) on 17 September 2000 in Sydney, Australia
 * CR: 57.96 swum by Jenny Thompson (USA) on 21 July 2003 in Barcelona, Spain