The Castle of Sancti Petri (Castilian: Piedras Santas) is a stronghold located in San Fernando, Province of Cádiz, Andalusia, southwestern Spain.

[1] During the 1st century, the Phoenicians settled on the island, founding a temple dedicated to Melqart, their god, .

The castle was in an advanced state of deterioration, but the authorities of the municipalities of San Fernando and Chiclana de la Frontera funded a major rehabilitation programme.

It was declared a Cultural Monument by Decree of April 22, 1949, and Law 16/1985, as a Spanish Historical Heritage landmark.

In 1993, the Andalusian authorities gave it special recognition amongst the castles of the Autonomous Community of Andalusia.