La Palma Castle (Castelo da Palma in Galician) is a defensive structure in the municipality of Mugardos, Ferrol region. It formed part of the 16th-century defensive system of the Ferrol estuary and has been listed as a Site of Cultural Interest since 1994.
Nearby stood San Martín Castle, of which only ruins remain. A heavy chain was stretched between them to block enemy ships from entering the estuary.
Its last function was as a military prison. Today the Mugardos Tourism Office organises guided visits.