The Castle of San Michele (Italian: Castello di San Michele) (Sardinian: Casteddu de Santu Miali) is a medieval castle in Cagliari, the capital of Sardinia, Italy.

The 1990s excavations have revealed the remains of a rural church, probably of the early medieval period, upon which was built the castle in the 12th century to defend the city of Santa Igia, the capital of the Giudicato of Cagliari.

Later it was abandoned and used as a hospital during the so-called "Plague of Saint Efisio" (1652-1656).

Around 1940, it was occupied by the Regia Marina (Italian Navy) and later become proprierty of the comune of Cagliari.

The castle has undergone a substantial modifications and now is used as a Center of Art and Culture.