The Women's 400m Individual Medley event at the 10th FINA World Aquatics Championships swam 27 July 2003 in Barcelona, Spain. Preliminary heats swam in the morning session, with the top-8 finishers advancing to swim again in the Final that evening. At the start of the event, the World (WR) and Championship (CR) records were: * WR: 4:33.59 swum by Yana Klochkova (Ukraine) on September 16, 2000 in Sydney, Australia. * CR: 4:36.10 swum by Petra Schneider (East Germany) on August 1, 1982 in Guayaquil, Ecuador