| Terzo | |
| Official Name: | Comune di Terzo |
| Coordinates: | 44.6667°N 33°W |
| Region: | Piedmont |
| Province: | Alessandria (AL) |
| Mayor: | Vittorio Giovanni Grillo |
| Area Total Km2: | 8.8 |
| Population Total: | 874 |
| Population As Of: | 2005[1] |
| Population Demonym: | Terzesi |
| Elevation M: | 222 |
| Postal Code: | 15010 |
| Area Code: | 0144 |
Terzo is a comune (municipality) in the Province of Alessandria in the Italian region Piedmont, located about 70km (40miles) southeast of Turin and about 30km (20miles) southwest of Alessandria.
It was a fortress of the bishop of Acqui, of which only a late medieval tower remains.Terzo borders the following municipalities: Acqui Terme, Bistagno, Melazzo, and Montabone.