The Moorish Castle is the name of a Medieval fortification made up of various buildings, gates, fortified walls and its most dominant features, the Tower of Homage and the Gate House. The former is clearly visible to all visitors to Gibraltar, not only because of its striking construction but also because of its dominant and strategic position.

The Tower of Homage is the highest tower of the Islamic period in the Iberian Peninsula, and the Castle's Qasbah is the largest in the area. The Castle itself played a prominent part in the Arab conquest of the Iberian Peninsula, which overran a large portion of it in two years - an invasion which led to Arab domination over part of Europe for over seven centuries. It is therefore of great heritage significance not only to Gibraltar and Iberia but also to Europe.

The present Tower of Homage, and most of what is visible today of the Castle, was rebuilt during the second Moorish period of occupation in the early 14th century, after its near destruction during a reconquest of Gibraltar by the Moors following a brief reoccupation by Spain (from 1309 to 1333).

Today the Moorish Castle is one of the major tourist attractions of Gibraltar and it features on the reverse of the 1995 design (still in circulation) for the £5 Gibraltar banknotes.

The term Moorish Castle or "El Castillo" in Spanish, is also used locally when referring to the residential area surrounding the Castle, which houses the Moorish Castle Estate.

Part of the castle itself also houses the HM Prison of Gibraltar.

The Great Siege Tunnels, St Michael's cave.