Palazzo Federico II, Medieval castle ruins in Calvi, Italy.

Palazzo Federico II is a castle ruin in Calvi featuring two stories built in Italian Gothic style, with pointed arches and carved stone details visible throughout. The structure combines different building methods from various periods.

Frederick II had the palace built at Cubante, probably in the early 1240s, as one of his loca solatiorum, hunting residences; it appears in the Statutum de reparatione castrorum (1241–1246) as «domus domini imperatoris Apicii». After the Hohenstaufen dynasty, Charles of Anjou ordered roof, door and window repairs in 1271 and 1274, giving the building fortified features and the name castrum. In 1593 the Spinelli bought it at auction, and Carlo III Spinelli restored it as a country residence, from which the name Casino del Principe derives.

The name "Casino del Principe" comes from the Spinelli princes of San Giorgio, who bought the palace at a judicial auction in 1593. Carlo III Spinelli restored it as a country residence in the early 18th century instead of moving to Naples. Local tradition long held that a solitary prince threw unwanted guests into the Calore through an underground passage.

The ruins stand in the rural locality of Cubante, in the municipality of Calvi, not in the town centre. They are reached by country roads, so a vehicle is useful; the site is a ruin with no facilities, and the surrounding land is private farmland.

Local tradition held that a solitary prince lived here and disposed of unwanted guests by throwing them through an underground passage into the Calore river. Historians also long confused the building's patron, wrongly attributing it to Frederick Barbarossa rather than Frederick II.