The Gibraltar Nature Reserve is a protected nature reserve in the British Overseas Territory of Gibraltar that covers over 40% of the territory's land area. It was established as the Upper Rock Nature Reserve in 1993 under the International Union for Conservation of Nature's category Ia and was last extended in 2013. It is known for its semi-wild population of Barbary macaques, and is an important resting point for migrating birds.

Originally from the Atlas Mountains and the Rif Mountains of Morocco, the Barbary macaque population in Gibraltar is the only wild monkey population on the European continent. Although most Barbary monkey populations in Africa are experiencing decline due to hunting and deforestation, the Gibraltar population is increasing. As of 2020, some 300 animals in five troops occupy the Upper Rock area of the Gibraltar Nature Reserve, though they make occasional forays into the town. As they are a tailless species, they are also known locally as Barbary apes or rock apes, despite being classified as monkeys. Spanish speakers simply refer to them as monos when conversing in Spanish, although English is the native language as the area is a British overseas territory.