Swimming at the 2007 World Aquatics Championships – Women's 4 × 100 metre medley relay

The Women's 4x100m Medley Relay at the 2007 World Aquatics Championships took place on 31 March 2007 at the Rod Laver Arena in Melbourne, Australia. The top-12 finishers from this race qualified for the event at the 2008 Olympics. 29 teams were entered in the event; all swam.

The existing records when the event started were: