| Castelmuzio | |
| Coordinates: | 43.1417°N 11.6594°W |
| Province: | Siena (SI) |
| Comune: | Trequanda |
| Elevation M: | 443 |
| Population Total: | 265 |
| Population As Of: | 2011 |
| Gentilic: | Castellini |
Castelmuzio is a village in Tuscany, central Italy, administratively a frazione of the comune of Trequanda, province of Siena. At the time of the 2001 census its population was 265.[1]
Castelmuzio is about 55 km from Siena and 8 km from Trequanda.