San Antón Castle is a 16th century castle that was part, together with the Castillo de Santa Cruz and the Castillo de San Diego, of a strategic network of castles and batteries to defend the city of A Coruña.

It was declared a Historic-Artistic Monument in 1949 and since 1994 it has come to be considered an Asset of Cultural Interest with the category of Monument.

This old fortress was built on what was then a small islet in the middle of the Coruña bay, where there was a small hermitage dedicated to San Antón. Its purpose was to defend the city from attacks from the sea. Its construction began in 1587, according to an inscription on the front of the fortress.

During the English attack of 1589 by the English Navy, the castle contributed effectively to the defense of the city, despite being unfinished. After the attack, its construction was continued until the completion of the works in 1590.

Starting in the 18th century, the fortress became a prison, a function that it would maintain until it was handed over to the City Council of La Coruña in 1960.

On the ground floor, former rooms of the castle garrison, pieces from the various periods of Prehistory and Ancient History of Galicia are exhibited, most of which come from archaeological excavations at sites in the province. Special mention should be made of the pre and protohistoric goldsmith collection, with such remarkable pieces as the helmet from the Bronze Age of Leiro, the torques of the San Lorenzo de Pastor castro, O Pino, or the Chalcolithic goldsmith ensemble of Cícere (necklace of straps, headbands and other pieces).

On the upper floor, which occupies the so-called Governor's House, where not only illustrious Galicians lived, such as Juana de Vega and her husband General Mina, but also predecessors of others such as Francisco Vázquez who would become mayor of the city, Some milestones in the history of the city are remembered: the expedition of the Invincible Armada and the subsequent attack by Drake in 1589, with the heroic intervention of María Pita, Captain Juan Varela, Captain Troncoso and many other people from Coruña and residents of the next few places.

In it, illustrious prisoners, such as Malaspina, Macanaz or Porlier, suffered imprisonment.

On May 30, 2009, in a documentary on regional television, there was talk of the possibility that Manuel Blanco Romasanta, the werewolf from Allariz, had died in this castle.