British Indian Ocean Territory - IO - IOT - South Asia

Last updated: April 10, 2024
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British Indian Ocean Territory Factbook Data

Dependency status

overseas territory of the UK; administered by a commissioner, resident in the Foreign, Commonwealth, and Development Office in London

Diplomatic representation from the US

embassy: none (overseas territory of the UK)

Geographic coordinates

6 00 S, 71 30 E;note - Diego Garcia 7 20 S, 72 25 E

Natural hazards

none; located outside routes of Indian Ocean cyclones

Area - comparative

land area is about one-third the size of Washington, DC


Formerly administered as part of the British Crown Colony of Mauritius, the British Indian Ocean Territory (BIOT) was established as an overseas territory of the UK in 1965. A number of the islands in the territory were later transferred to the Seychelles when it gained independence in 1976. Subsequently, BIOT has consisted of the six main island groups that make up the Chagos Archipelago. Only Diego Garcia, the largest and most southerly of the islands, is inhabited. It contains a joint UK-US naval support facility and hosts one of four dedicated ground antennas that assist in the operation of the Global Positioning System (GPS) navigation system -- the others are on Kwajalein (Marshall Islands); at Cape Canaveral, Florida (US); and on Ascension Island (Saint Helena, Ascension, and Tristan da Cunha). The US Air Force also operates a telescope array on Diego Garcia as part of the Ground-Based Electro-Optical Deep Space Surveillance System (GEODSS) for tracking orbital debris, which can be a hazard to spacecraft and astronauts.

Between 1967 and 1973, the former agricultural workers who lived on the islands were relocated, primarily to Mauritius but also to the Seychelles. Negotiations with the UK between 1971 and 1982 resulted in the establishment of a trust fund to compensate the displaced islanders, known as Chagossians. Beginning in 1998, the islanders pursued a series of lawsuits against the British Government, seeking further compensation and the right to return to the territory. British court rulings in 2006 and 2007 invalidated immigration policies that had excluded the islanders from the archipelago, but in 2008, the House of Lords -- the final court of appeal in the UK -- ruled in favor of the British Government by overturning the lower court rulings and finding no right of return for the Chagossians. In 2015, the Permanent Court of Arbitration unanimously held that the marine protected area that the UK declared around the Chagos Archipelago in 2010 violated the UN Convention on the Law of the Sea.

In 2019, the International Court of Justice ruled in an advisory opinion that Britain’s decolonization of Mauritius was not lawful because of continued Chagossian claims. A non-binding 2019 UN General Assembly vote demanded that Britain end its “colonial administration” of the Chagos Archipelago and that it be returned to Mauritius. UK officials continue to defend Britain's sovereignty over the islands and argue that the issue is a bilateral dispute between Mauritius and the UK that does not warrant international intervention. 

Environment - current issues

wastewater discharge into the lagoon on Diego Garcia

Military and security forces

no regular military forces


tropical marine; hot, humid, moderated by trade winds


698 km

Exchange rates

the US dollar is used

Executive branch

chief of state: King CHARLES III (since 8 September 2022)

head of government: Commissioner Paul CANDLER (since 8 July 2021); Administrator Balraj DHANDA; note - both reside in the UK and are represented by Commander Colvin OSBORN, RN, Officer commanding British Forces on Diego Garcia (since January 2022)

cabinet: NA

elections/appointments: the monarchy is hereditary; commissioner and administrator appointed by the monarch

Flag description

white with six blue wavy horizontal stripes; the flag of the UK is in the upper hoist-side quadrant; the striped section bears a palm tree and yellow crown (the symbols of the territory) centered on the outer half of the flag; the wavy stripes represent the Indian Ocean; although not officially described, the six blue stripes may stand for the six main atolls of the archipelago

Land boundaries

total: 0 km

Land use

agricultural land: 0% (2018 est.)

arable land: 0% (2018 est.)

permanent crops: 0% (2018 est.)

permanent pasture: 0% (2018 est.)

forest: 0% (2018 est.)

other: 100% (2018 est.)

Legal system

the laws of the UK apply where applicable

Maritime claims

territorial sea: 12 nm

Environment (Protection and Preservation) Zone: 200 nm

International organization participation


Natural resources

coconuts, fish, sugarcane

Geography - note

note 1: archipelago of 55 islands; Diego Garcia, the largest and southernmost island, occupies a strategic location in the central Indian Ocean; the island is the site of a joint US-UK military facility

note 2: Diego Garcia is the only inhabited island of the BIOT and one of only two British territories where traffic drives on the right, the other being Gibraltar

Economic overview

small island territory economy; economic activity mainly on Diego Garcia with national military installations; recently settled disputes with Mauritius have increased oil exports; established marine reserve has limited commercial fishing

Ports and terminals

major seaport(s): Diego Garcia

Telecommunication systems

general assessment: separate facilities for military and public needs are available (2018)

domestic: all commercial telephone services are available, including connection to the Internet (2018)

international: country code (Diego Garcia) - 246; landing point for the SAFE submarine cable that provides direct connectivity to Africa, Asia and near-by Indian Ocean island countries; international telephone service is carried by satellite (2019)


flat and low coral atolls (most areas do not exceed two m in elevation); sits atop the submarine volcanic Chagos-Laccadive Ridge

Military - note

defense is the responsibility of the UK; in November 2016, the UK extended the US lease on Diego Garcia until December 2036

Country name

conventional long form: British Indian Ocean Territory

conventional short form: none

abbreviation: BIOT

etymology: self-descriptive name specifying the territory's affiliation and location


archipelago in the Indian Ocean, south of India, about halfway between Africa and Indonesia

Map references

Political Map of the World

Diplomatic representation in the US

none (overseas territory of the UK)

Internet country code


Broadcast media

Armed Forces Radio and Television Service (AFRTS) broadcasts over 3 separate frequencies for US and UK military personnel stationed on the islands

Communications - note

Diego Garcia hosts one of four dedicated ground antennas that assist in the operation of the Global Positioning System (GPS) navigation system (the others are on Kwajalein (Marshall Islands), at Cape Canaveral, Florida (US), and on Ascension Island (Saint Helena, Ascension, and Tristan da Cunha))

Disputes - international

Mauritius and Seychelles claim the Chagos Islands; negotiations between 1971 and 1982 resulted in the establishment of a trust fund by the British Government as compensation for the displaced islanders, known as Chagossians, who were evicted between 1967-73; in 2001, the former inhabitants of the archipelago were granted UK citizenship and the right of return; in 2006 and 2007, British court rulings invalidated the immigration policies contained in the 2004 British Indian Ocean Territory Constitution Order that had excluded the islanders from the archipelago; in 2008, a House of Lords' decision overturned lower court rulings, once again denying the right of return to Chagossians; in addition, the UK created the world's largest marine protection area around the Chagos islands prohibiting the extraction of any natural resources therein


highest point: ocean-side dunes on Diego Garcia 9 m

lowest point: Indian Ocean 0 m

Age structure

0-14 years: NA

15-64 years: NA

65 years and over: NA

Contraceptive prevalence rate



name: administered from London; often regarded as being on Diego Garcia

geographic coordinates:  7 18S, 12 24E

time difference: UTC+6 (12 hours ahead of Washington, DC, during Standard Time)

Current health expenditure


Drinking water source

improved: urban: NA

rural: NA

total: NA

unimproved: urban: NA

rural: NA

total: NA

Exports - commodities

tuna and other fish, computers, integrated circuits, diamonds, jewelry (2021)


history: British Indian Ocean Territory (Constitution) Order 2004

Dependency ratios

total dependency ratio: NA

youth dependency ratio: NA

elderly dependency ratio: NA

potential support ratio: NA

National anthem

note: as an overseas territory of the United Kingdom, "God Save the King" is official (see United Kingdom)

Exports - partners

Singapore 69%, United States 10%, Canada 5%, Ireland 4%, Saudi Arabia 2% (2021)

Imports - commodities

inedible fish and animal products, aluminum structures, cement, boat propellers, packaged medicines (2021)

Imports - partners

Singapore 64%, United States 22%, Panama 4%, Ireland 3%, Bulgaria 1% (2021)


no indigenous inhabitants

note: approximately 1,200 former agricultural workers resident in the Chagos Archipelago, often referred to as Chagossians or Ilois, were relocated to Mauritius and the Seychelles in the 1960s and 1970s; approximately 3,000 UK and US military personnel and civilian contractors living on the island of Diego Garcia (2018)


total: 60 sq km

land: 60 sq km (44 Diego Garcia)

water: 54,340 sq km

note: includes the entire Chagos Archipelago of 55 islands


note: short section of paved road between port and airfield on Diego Garcia


1 (2024)

Death rate


Birth rate


Children under the age of 5 years underweight


Education expenditures