The Women's 100m Butterfly event at the 10th FINA World Aquatics Championships swam 20–21 July 2003 in Barcelona, Spain. Preliminary[1] heats swam in the morning session of 20 July, with the top-16 finishers advancing to semifinal[2] heats that evening. The top-8 finishers from the Semifinals then advanced to swim again in the Final[3] the next evening.
At the start of the event, the World (WR) and Championship (CR) records were:
WR: 56.61 swum by Inge de Bruijn (Netherlands) on September 17, 2000 in Sydney, Australia.