| Petroio | |
| Coordinates: | 43.1453°N 11.6881°W |
| Province: | Siena (SI) |
| Comune: | Trequanda |
| Elevation M: | 447 |
| Population Total: | 404 |
| Population As Of: | 2011 |
| Gentilic: | Petroiani |
Petroio 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 335.[1]
Petroio is about 50 km from Siena and 7 km from Trequanda.