Swimming at the 2009 World Aquatics Championships – Women's 4 × 100 metre medley relay
The Women's 4x100m Medley Relay at the 2009 World Aquatics Championships took place on August 1, 2009 at the Foro Italico in Rome, Italy.
Medalists
Records
The existing records when the event started were:| Record | Swimmer | Time | Location |
| World record | Emily Seebohm Leisel Jones Jessicah Schipper Lisbeth Trickett | 3:52.69 |  Beijing 2008 |
| Championship record | Emily Seebohm Leisel Jones Jessicah Schipper Lisbeth Lenton | 3:55.74 |  Melbourne 2007 |