Casei Gerola is a comune (municipality) in the Province of Pavia, Lombardy, Italy. It is located about 60 km southwest of Milan and about 25 km southwest of Pavia. Casei Gerola borders the following municipalities: Castelnuovo Scrivia, Cornale e Bastida, Isola Sant'Antonio, Mezzana Bigli, Molino dei Torti, Pontecurone, Silvano Pietra, Voghera. It was part of the Counties of Guastalla and, later, county of Montechiarugolo, both ruled by the Torelli family, until 1612. It remained to the Torelli until 1797.

Demographic evolution