A condominium (plural either condominia, as in Latin, or condominiums) in international law is a territory (such as a border area or a state) in or over which multiple sovereign powers formally agree to share equal dominion and exercise their rights jointly, without dividing it into "national" zones.
Although a condominium has always been recognized as a theoretical possibility, condominia have been rare in practice. A major problem, and the reason so few have existed, is the difficulty of ensuring co-operation between the sovereign powers; once the understanding fails, the status is likely to become untenable. For example, disputes over the status of the Condominium of Bosnia-Herzegovina, nominally governed by both the Ottoman Empire and Austro-Hungarian Empire, caused the Bosnian Crisis, a cause of World War I.
Etymology
The word is recorded in English since 1718, from Modern Latin, apparently coined in Germany c. 1700 from Latin con- 'together' + dominium 'right of ownership' (compare domain). A condominium of three sovereign powers is sometimes called a tripartite condominium or tridominium.
Current condominia
Condominium Sovereign states responsible Area (km2) Population Date created Notes Abyei Area 10,546 124,390 The 2005 Comprehensive Peace Agreement, which ended the Second Sudanese Civil War, created the special status administrative area which is considered to simultaneously be part of West Kordofan state and Northern Bahr el Ghazal state. Following the independence of South Sudan in 2011, the area effectively became a condominium between the Republic of South Sudan and the Republic of the Sudan. Antarctica 29 state parties 14,200,000 1,300–5,100 (seasonal) Antarctica is a de facto continental condominium, governed by the 29 state parties to the Antarctic Treaty that have consulting status. Only seven of these state parties have territorial claims. Brčko District : Federation of Bosnia and Herzegovina 493 83,516 Subnational condominium of the two entities of Bosnia and Herzegovina created due to its multiethnic nature. Gulf of Fonseca 3,200 0 https://www.un.org/oceancapacity/sites/www.un.org.oceancapacity/files/thesis_vlezama.pdf&ved=2ahUKEwjkq7jhvNCEAxVyh_0HHfwSCRsQFnoECBMQBg&usg=AOvVaw25iNG9sqx7La7xvd94-ATj El Salvador, Honduras, and Nicaragua exercise a tripartite condominium over parts of the Gulf of Fonseca and of the territorial sea outside its mouth. Joint Regime Area 0 As an alternative to delimiting their sea boundary, Colombia and Jamaica share a maritime condominium called the Joint Regime Area in the Caribbean Sea by mutual agreement. The outer portion of the EEZ of each country otherwise would overlap in this area. Unlike other "joint development zones", this condominium appears not to have been purposed simply as a way to divide oil, fisheries or other resources. Koalou 68 c. 5,000 The area is administrated jointly by the "Joint Committee for the Concerted Management of the Kourou/Koalou Area" (COMGEC-K). Neither nation expresses sovereignty over the area, with a permanent solution still pending. Lake Constance 536 0 No official treaty Austria and Germany consider themselves to hold a tripartite condominium with Switzerland (albeit on different grounds) over the main part of Lake Constance (without its islands). On the other hand, Switzerland holds the view that the border runs through the middle of the lake. Hence, no international treaty establishes where the borders of Switzerland, Germany, and Austria, in or around Lake Constance, lie. Lake Titicaca 8,372 0 Lake Titicaca between Bolivia and Peru was originally divided between the two countries. In 1951, however, Peruvian President Manuel A. Odría declared that "waters of Lake Titicaca belong in indivisible condominium to Peru and Bolivia". An agreement from 1955 declares "the indivisible and exclusive joint ownership of both countries of the waters of the lake", while a subsequent agreement from 1957 describes an "indivisible and exclusive condominium over the waters of Lake Titicaca". However, while these agreements were initially signed in the 1950s, they were not ratified by Bolivia until 1987. Moselle 0.723 0 The Moselle and its tributaries, the Sauer and the Our, constitute a condominium between Germany and Luxembourg, which also includes bridges, about 15 river islands of varying size, and the tip of one island, Staustufe Apach, near Schengen (the rest of the island is in France). MOU 74 Box 50,000 0 Officially known as the Australia–Indonesia Memorandum of Understanding, the MOU 74 Box was established by a bilateral agreement regarding the Operations of Indonesian Traditional Fishermen in Areas of the Australian Fishing Zone and Continental Shelf – 1974. The agreement recognizes access rights of traditional Indonesian fishers from Rote Ndao Regency in shared waters to the north of Australia with regard to the long history of traditional Indonesian fishing there, especially for trepang, trochus, abalone and sponges. The MOU 74 Box includes the Ashmore and Cartier Islands, Browse Island, and Scott and Seringapatam Reefs. Paraná River 0 The Paraná River between Brazil and Paraguay, starting from the former location of the Guaíra Falls (now the location of the Itaipu Dam) to the mouth of the Iguazu River, was declared a condominium so that the two countries could jointly utilize the river for the production of hydroelectric power. The 1973 treaty establishing the condominium created a binational governing entity called ITAIPU, made up of both Brazilian and Paraguayan officials. Pheasant Island 0.00682 0 Pheasant Island is an island of the Bidassoa. Established as part of the Treaty of the Pyrenees, It is formally administered by Spain between 1 February and 31 July each year (181 or 182 days) and by France between 1 August and 31 January each year (184 days)."The island that switches countries every six months". . BBC News. 28 January 2018. Retrieved 28 January 2018.Río de la Plata35,500019 November 1973Signed in Montevideo the 1973 Boundary Treaty between Uruguay and Argentina defined the geographical limits of the Rio de la Plata and created a joint jurisdiction regime. Beyond 7 nautical miles off the river shores sovereignty is shared between the two countries with a boundary line defined only to be applicable to the riverbed and subsoil resources. Tort-Kocho 0 Tort-Kocho is a road which connects the Tajikistani Vorukh exclave in Kyrgyzstan to the rest of Tajikistan. Prior to 2025, both the Kyrgyz and Tajikistani considered the road part of their sovereign territory. The road was contested during the 2021 Kyrgyzstan–Tajikistan clashes when Tajik administrators blocked the Osh–Batken–Isfana road demanding the Tort-Kocho road be unblocked by Kyrgyzstan. As part of the 2025 delimitation of the Kyrgyzstan–Tajikistan border, the wide roadbed and a "security zone" were declared neutral territory, with Kyrgyzstani politician Kamchybek Tashiev saying the road will not belong to "either the Kyrgyz or Tajik side". Yacyretá Dam 0 The Treaty of Yacyretá, signed 1973 and coming into force 1974, establishes joint governance between Argentina and Paraguay of the Yacyretá Dam in the Paraná River. It states that "the installations of the hydroelectric scheme and their auxiliary works, together with the installations for the improvement of navigability on the River Parana. . .shall constitute a condominium, with equal shares, of both the High Contracting Parties".
Co-principality
Under French law, Andorra was once considered to be a French–Spanish condominium, although it is more commonly classed as a co-principality, since it is itself a sovereign state, not a possession of one or more foreign powers. However, the position of head of state is shared ex officio by two foreigners, one of whom is the President of France, currently Emmanuel Macron, and the other the Bishop of Urgell in Spain, currently Josep-Lluís Serrano Pentinat.
Former condominia
Allied-occupied Germany from 1945 until 1949 and Berlin after that until 1991 were under the control of the Allied Control Council, which consisted of representatives from Britain, France, the Soviet Union and the United States. In 688 the Byzantine Emperor Justinian II and the Umayyad Caliph Abd al-Malik ibn Marwan reached an unprecedented agreement to establish a condominium (the concept did not yet exist) over Cyprus, with the collected taxes from the island being equally divided between the two parties. The arrangement lasted for some 300 years, even though in the same time there was nearly constant warfare between the two parties on the mainland. Fellesdistriktet (, literally "The common area", ) was a Russo-Norwegian condominium comprising Sør-Varanger Municipality and the Pechengsky District from 1684 until 1826. Anglo-Egyptian Sudan was legally an Egyptian-British condominium from 1899 until 1956, although de facto, the Khedivate, Sultanate, and Kingdom of Egypt played no role in its government other than providing some administrators in the country: all political decisions were made by the United Kingdom and all Governors-General of Anglo-Egyptian Sudan were British. The system was resented by Egyptian and Sudanese nationalists, and would later be disavowed by the Egyptian Government, although it persisted due to the United Kingdom's effective control over Egypt itself, which began from 1882 and continued until at least 1936. The Colony of Caiena and Guiana became a condominium between Brazil and Portugal upon the elevation of Brazil to the status of an equal kingdom in 1815 until the return of the territory to France in 1817. The Condominium of Bosnia and Herzegovina was jointly ruled by Cisleithanian Austria and Transleithanian Hungary between 1908 and 1918, while both countries were parts of the Austro-Hungarian Empire. An islet in the border river Brömsebäck was considered to belong to neither (or both) Denmark and Sweden. The Duchy of Courland was a condominium of the Grand Duchy of Lithuania and the Crown of Poland from 1726 until 1795. The Independent State of Croatia during World War II from 1941 to 1943 was a military condominium of Nazi Germany and Fascist Italy until 1943, when Italy split between the Allied-leaning Kingdom of Italy under King Victor Emmanuel III and Axis-leaning Italian Social Republic under Benito Mussolini.Jozo Tomasevich. "The Chetniks". War and Revolution in Yugoslavia. Stanford University Press, 1975. p. 103. "The condominium in Croatia was the most important example of Italo-German collaboration in controlling and despoiling an occupied area [...]".Stephen R. Graubard, (ed.).Exit from Communism. Transaction Publishers, 1993. pp. 153–154. "After the Axis attack on Yugoslavia in 1941, Mussolini and Hitler installed the Ustašas in power in Zagreb, making them the nucleus of a dependent regime of the newly created Independent State of Croatia, an Italo-German condominium predicated on the abolition of Yugoslavia." Günay Göksu Özdoğan, Kemâli Saybaşılı. Balkans: a mirror of the new international order. Marmara Üniversitesi. Dept. of International Relations, 1995. p. 143. "Croatia (with Bosnia-Hercegovina) formally became a new Axis ally – the Independent State of Croatia (NDH). This was in fact, Italo-German condominium, [...]".John R. Lampe (ed.), Mark Mazower (ed.). Ideologies and National Identities: The Case of Twentieth-Century Southeastern Europe. Central European University Press, 2003. p. 103. "[...] the Independent State of Croatia (hereafter NDH, Nezavisna Drzava Hrvatska), in reality an Italo-German condominium [...]" Canton and Enderbury Islands were a British–American condominium from 1939 until 1979 when they became part of Kiribati. Couto Misto was shared until 1864 between Spain and Portugal, even though in its final decades of existence it was de facto independent. Egypt from 1876 to 1882 was under France and the United Kingdom.