Montjuic Castle is a former military fortress located on the mountain of Montjuic, in the city of Barcelona.

The fortress was a Spanish Army installation, although it was later ceded to the city council, which currently manages it. Historically, the castle has played an important role in several episodes in Barcelona's history.

The first construction that occupied the top of this mountain was a watchtower designed to signal the proximity of ships approaching the city.

In 1640, during the revolt against Philip IV, the first fortification was built on Montjuic, in the form of an earthen quadrilateral covered with stone and mud. This provisional fortification served to repel the assault by the Castilian troops commanded by the Marquis of Vélez on 26 January 1641. The original fort was converted into a castle in 1694. Its plan occupied the entire flat part of the summit, with three bastions facing landward and a saw-toothed line facing the sea. The previous small fortification remained as an inner redoubt.

During the War of the Spanish Succession, the fall of the castle into the hands of the Duke of Peterborough on 17 September 1705 was a factor that influenced the Catalonians to side with Archduke Charles of Austria.

Recovered on 25 April 1706 by Philip V, he lost it again on 12 May of the same year, and it was not in his hands again until 12 September 1714 when, in accordance with the fifth article of the Capitulations proposed that same day by the Duke of Berwick, the castle was handed over to the Bourbon troops.

In 1751, the military engineer Juan Martín Cermeño ordered the destruction of the old fort of 1640 and finished shaping the complex of buildings, providing it with services and cisterns, one of them for drinking water, and ordered the construction of the moat.

Between 1779 and 1799, various works were carried out, including those necessary to double the number of men, as well as the construction of kitchens for 3,000 people; the castle then took the form it has today. It was equipped with artillery with no less than 120 cannons.