Castelmagno is a small comune (municipality) in the Province of Cuneo in the Italian region of Piedmont, located about 80 kilometres (50 mi) southwest of Turin and about 25 kilometres (16 mi) west of Cuneo.

The population of the municipality of Castelmagno is divided between the frazioni (hamlets) of Einaudi, Campomolino, Colletto, Nerone, Chiotti and Chiappi; "Castelmagno" is the name of the municipal entity, not corresponding to any hamlet. The main attraction is the sanctuary of San Magno, at an elevation of 1,761 metres (5,778 ft) above sea level.