Swimming at the 2003 World Aquatics Championships – Women's 4 × 100 metre freestyle relay

The women's 4x100m freestyle relay event at the 10th FINA World Aquatics Championships swam 20 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: 3:36.00 swum by Germany on July 29, 2002 in Berlin, Germany.
 * CR: 3:37.91 swum by China on September 7, 1994 in Rome, Italy