The British Indian Ocean Territory (BIOT) is an Overseas Territory of the United Kingdom situated in the Indian Ocean, halfway between Tanzania and Indonesia. The territory comprises the seven atolls of the Chagos Archipelago with over 1,000 individual islands, many very small, amounting to a total land area of 60 square kilometres. The largest and most southerly island is Diego Garcia, 27 square kilometres, the site of a Joint Military Facility of the United Kingdom and the United States. Official administration is remote from London, though the local capital is often regarded as being on Diego Garcia.

The British Overseas Territories (BOTs) are the 14 territories with a constitutional and historical link with the United Kingdom that, while not forming part of the United Kingdom itself, are part of its sovereign territory. The permanently inhabited territories are delegated varying degrees of internal self-governance, with the United Kingdom retaining responsibility for defence, foreign relations and internal security, and ultimate responsibility for good governance. All of the territories are inhabited by civilians, except three that are chiefly or only inhabited by military or scientific personnel. All fourteen have the British monarch as head of state. These UK government responsibilities are assigned to various departments of the Foreign, Commonwealth and Development Office and are subject to change.