| Montecastrilli | |
| Official Name: | Comune di Montecastrilli |
| Native Name: | Montes Carsulis |
| Coordinates: | 42.65°N 41°W |
| Region: | Umbria |
| Province: | Terni (TR) |
| Frazioni: | Casteltodino, Farnetta, Collesecco, Castel dell'Aquila |
| Mayor: | Fabio Angelucci |
| Area Total Km2: | 62.43 |
| Population Footnotes: | [1] |
| Population Total: | 5026 |
| Population As Of: | 30 November 2017 |
| Population Demonym: | Montecastrillesi |
| Elevation M: | 391 |
| Saint: | St. Nicholas of Myra |
| Day: | December 6 |
| Postal Code: | 05026 |
| Area Code: | 0744 |
Montecastrilli is a comune (municipality) in the Province of Terni in the Italian region of Umbria, located about 50 km south of Perugia and about 15 km northwest of Terni.
Among the churches in the town are: