The Great Siege Tunnels in the British Overseas Territory of Gibraltar, also known as the Upper Galleries, are a series of tunnels inside the northern end of the Rock of Gibraltar. They were dug out from the solid limestone by the British during the Great Siege of Gibraltar of the late 18th century.

The Rock of Gibraltar is a highly strategic monolithic limestone mountain 426 m (1,398 ft) high dominating the western entrance to the Mediterranean Sea. It is situated near the end of a narrow 9 kilometres (5.6 mi) long promontory stretching due south into the Mediterranean Sea and is located within the British territory of Gibraltar, and is 27 km north-east of Tarifa, Spain, the southwestern tip of Europe on the Iberian Peninsula. The rock serves as an impregnable fortress and contains a labyrinthine network of man-made tunnels known as the Tunnels of Gibraltar. Most of the Rock's upper area comprises a nature reserve which is home to about 300 Barbary macaques. It is a major tourist attraction.