Spain and the United Kingdom are in dispute over which piece of territory?

The United Kingdom and Spain are in a dispute over the sovereignty of the British Overseas Territory of Gibraltar. Gibraltar is a small peninsula located at the southern tip of Spain, and has been a British possession since 1713. Spain has long claimed that Gibraltar should be returned to Spanish control, while the UK maintains that the people of Gibraltar have a right to self-determination and have consistently voted in referendums to remain British.