The Fortress of El Castro is a fortification located in Vigo, Spain built in 1665 by the Spanish Empire in the province of Pontevedra during the Portuguese Restoration War to defend the region from potential attacks by English forces.

[1] Built on a hill of the same name, the defensive system of Vigo consisted of the fortresses of O Castro and San Sebastián along with the city wall.

Despite this effort to provide security to the city, documents from that time say that this defensive system was ineffective as it could not impede landings further along the coast.

In 1809, the fortress was occupied by the French Imperial Army during Peninsular War; on 28 March of that year, the fortress was reconquered by Spanish forces following an uprising by people of Vigo; as a result, the city was given the honorific title of "the faithful, loyal and courageous city of Vigo" the following year.

Nowadays the fortress is one of the preferred sites for people to take a walk in Vigo, because of its beautiful gardens, open spaces, fountain and also the privileged views.