Castel San Giovanni (Piacentino: Castél San Giuàn) is a town and comune in the province of Piacenza, Emilia-Romagna, Italy.

The origins of the town are probably related to an ancient pieve called Olubra and a fortress called Castellus Milonus, which preceded the construction of a new castle by Alberto Scoto in 1290 (now also disappeared).

After a period under the Dal Verme family of lords-condottieri, it became part of the Duchy of Parma and Piacenza in 1485.

Castel San Giovanni is twinned with:

This article on a location in Emilia–Romagna is a stub.