Castelletto d'Erro

Castelletto d'Erro is a comune (municipality) in the Province of Alessandria in the Italian region Piedmont, located about 70 km southeast of Turin and about 35 km southwest of Alessandria.

Castelletto d'Erro borders the following municipalities: Bistagno, Cartosio, Melazzo, Montechiaro d'Acqui, and Ponti.