List of divided islands
Sea islands 
Lake islands 
- Among Norway, Sweden and Finland:
- Between the United States and Canada:
- Between Norway and Russia:
- Between Finland and Russia:
- Äikkäänniemi in Nuijamaanjärvi
- Suursaari and a smaller island in Yla-Tirja
- Tarraassiinsaari, Härkäsaari, and Kiteensaari in Melaselänjärvi
- Island in Virmajärvi
- Rajasaari in Kokkojärvi
- Kalmasaari in Vuokkijärvi
- Varposaari in Hietajärvi
- Parvajärvensaari in Parvajärvi
- Keuhkosaari in Pukarijärvi / Ozero Pyukharin
- Siiheojansuusaari and Tossensaari in Onkamojärvi / Ozero Onkamo
- Between Finland and Norway:
- Between Sweden and Norway:
- Island in Sör Vammsjön/Vammen Søndre
- Hisön/Hisøya in Norra Kornsjön/Nordre Kornsjø (≈0,09 km²)
- Kulleholmen/Kalholmen (≈5500 m²) and Tagholm/Tåkeholmen (≈600 m²) in Södra Boksjön/Søndre Boksjø
- Salholmen and Trollön in Stora Le/Store Le
- Island in Tannsjøen/Tannsjön
- Linneholmene in Helgesjö
- Jensøya in Holmsjøen
- Storøya in Utgardsjøen
- Fallsjøholmen in Fallsjøen (Nordre Røgden)
- Island in Kroksjøen
- Island in Vonsjøen
- Island in Skurdalssjøen/Kruehkiejaevrie
- Island in a lake at altitude 710m on the Gihcijoka river
- Three islands in Čoarvejávri
- Between Lithuania and Belarus:
- Between the United Kingdom and Ireland:
- Pollatawny in Lough Vearty.
- Between Ethiopia and Djibouti:
- The border between Austria and Hungary cuts across the Neusiedler See/Fertő tó, where the water level fluctuates, sometimes exposing island flats which straddle the border.
River islands 
- Island in the Moselle River near Schengen: mostly in France, the tip is in the Moselle condominium shared by Luxembourg and Germany
- Bolshoy Ussuriyskiy (Heixiazi) at the confluence of the Ussuri and Amur rivers, between the People's Republic of China and Russia.
- Bolshoy (Abagaitu) at the Argun River, between the People's Republic of China and Russia.
- Corocoro Island in the delta of the Barima River: split between Venezuela and Guyana
- San Jose Island, Rio Negro: between Colombia and Brazil.
- The island complex Martín García - Timoteo Domínguez in the Río de la Plata between Argentina and Uruguay.
- The lower reaches of the Ganges, Teesta, and Brahmaputra Rivers, approaching the Ganges Delta, are braided and contain numerous sand islands called chars. These can be large and inhabited but are impermanent. At any given time, several are likely to straddle the border between India (Assam and West Bengal) and Bangladesh, though this border is not fully specified.
- An island labelled 'Q' in the Maritsa River, between Greece and Turkey.
- An islet in the Uutuanjoki, between Finland and Norway.
- An islet in the Vadet near Tunnsjø, between Norway and Sweden.
- An islet on the western side of the golf course that straddles the municipalities of Tornio in Finland, and Haparanda in Sweden is crossed by the international border.
- An islet in the Euphrates River on the border of Iraq and Syria.
- An area between the Orinoco and the Casiquiare - Rio Negro - Amazone shared by Venezuela, Guyana, Suriname, France and Brazil is the largest river bifurcation (splitting) in the world.
Historically divided islands 
Other islands have been divided by international borders in the past but they are now unified.
The definite borders of modern nation-states do not apply in other forms of societal organisation, where "divided" islands may consequently be less noteworthy. For example, in Ancient Greece, the island of Euboea was divided among several city states, including Chalcis and Eretria; and before its settlement by Europeans, the Island of Tasmania was divided among nine indigenous tribes.
Examples of formerly divided islands include:
- Corsica - was divided between the Republic of Pisa and the Republic of Genoa by a ruling by Pope Innocent II in 1132, and it remained so until the Battle of Meloria of 1284. Then Corsica successively became part of Genoa, Aragon, Genoa again, the Corsican Republic, France, Anglo-Corsican Kingdom, and France again, where it remains as of 2012.
- Sardinia - was divided into indigenous giudicati since before the year 900 through the extinction of the Giudicato of Arborea in 1420. Since then, Sardina has successively has been part of Aragon, the Spanish Empire, Piedmont-Sardinia, the Kingdom of Italy, and the Republic of Italy.
- Saaremaa (1237-1570) and Hiiumaa (1254-1563) - Divided between the Livonian Order and the Bishopric of Ösel-Wiek (the Kingdom of Denmark after 1560). Thereafter these were part of Denmark (Saaremaa only), the Kingdom of Sweden, Imperial Russia, Estonia, the U.S.S.R., Nazi Germany (1941–44), the U.S.S.R. again, and finally Estonia after the dissolution of the U.S.S.R. in 1991.
- Tobago - from 1654 through 1659, this island had colonies from both the Duchy of Courland and Semigallia and the Dutch Republic. Both of these colonies failed economically and were abandoned. Later, Tobago became part of the French Empire, then the Kingdom of Great Britain (1706), the United Kingdom of Great Britain and Ireland, the present United Kingdom, and the independent country of Trinidad and Tobago.
- Ternate - divided between the Spanish Empire allied with Tidore, and the Dutch Republic allied with the Sultan of Ternate from 1607 through 1663. Later, Ternate has successive been owned by the Netherlands, the Japanese Empire (1942–45), Netherlands again, and the independent country of Indonesia, beginning in 1949.
- Long Island, New York - divided between the Dutch Republic and the Kingdom of England beginning in 1640 (de facto, by the founding of the Southold), or in 1650 (de jure, by the Treaty of Hartford), through to the surrender of New Netherland to the British Army in 1664. Thereafter, Long Island has been owned by Kingdom of England, the United Kingdom, and the United States from 1781 through the present. Long Island has been part of the State of New York since 1781, and it is the largest island in the Contiguous United States (48 states).
- Great Britain - Earlier divided into three or more kingdoms, including England, Wales, and Scotland, and sometimes ruled in part by the Roman Empire and the Danish Empire. These parts were reduced to just two before 1707, when the Kingdom of England and the Kingdom of Scotland enacted the Acts of Union of 1707, establishing just one monarchy and one parliament. Since 1707, England, Scotland, and Wales have been part of (successively) the Kingdom of Great Britain, the Kingdom of Great Britain and Ireland, and the Kingdom of Great Britain and Northern Ireland, often called the United Kingdom for short.
- Newfoundland Island - Earlier divided between Great Britain and the French Empire until the enactment of the Treaty of Utrecht in 1713. Following this treaty, Newfoundland was part of the British Empire. Then it became the partially independent Dominion of Newfoundland, which next became a Province of Canada in 1949.
- Saint Kitts - Divided between Great Britain and the French Empire from 1626 through the Treaty of Utrecht in 1713. Then it became part of the British Empire for about 250 years, and finally part of the independent country of Saint Kitts and Nevis. At various times of war in the Caribbean Sea, either France or Great Britain occupied all of Saint Kitts both before and after 1713.
- Elba - divided from 1548 through 1802. Portoferraio belonged to the Duke of Florence (later the Grand Duchy of Tuscany) from 1548 until this was ceded to France in 1802 under the Treaty of Amiens. Porto Longone belonged to the State of Presidi, a client of first the Spanish Empire and then the Kingdom of Naples, from 1557 until ceded to France in 1801 by the Treaty of Florence. The rest of this island belonged to the Principality of Piombino until conquered by the French Empire, and then in 1802 Napoleon made Elba into the Kingdom of Etruria. This island was successively part of the French Empire, the Principality of Piombino under Elisa Baciocchi, under the sovereignty of Napoleon -- by the terms of the Treaty of Fontainebleau (1814), part of Tuscany again, part of the Kingdom of Italy, Italian Social Republic (1943–44), and finally part of the Republic of Italy.
- Efate - Divided for several months during 1889 between Franceville and the New Hebrides, then under an Anglo-French joint naval commission.
- Sakhalin Island - Divided between the Russian Empire, then the U.S.S.R., and the Japanese Empire along the 50th parallel north by the terms of the Treaty of Portsmouth of 1905 through the final Surrender of the Japanese Empire in 1945. Henceforth, all of Sakhalin became part of the U.S.S.R., and then the Russian Federation, de facto. The Japanese Empire still considers the ownership of Sakhalin to be undetermined, and Sakhalin is shown on many Japanese maps as a "no man's land".
- Killiniq Island - divided between Canada and the Colony of Newfoundland and then the Dominion of Newfoundland beginning with the Founding of Canada in 1867 through 1949 with the addition of Newfoundland to Canada.
- Ankoko Island in the Cuyuni River on the border between Venezuela and British Guiana (now Guyana).
- Zhongshan Dao in the Pearl River Delta was divided between China and Macau from ratification of the Treaty of Tientsin in 1862 through the final return of Macao to China in the year 1999.
A few former islands have disappeared because of changes in water levels:
- Vozrozhdeniya Island in the Aral Sea was split between the Soviet Republics of Uzbekistan and Kazakhstan. This border became an international one in 1991 when the U.S.S.R. was dissolved. By the year 2002, this island had become a peninsula of the mainland because of the falling water level of the Aral Sea.
- The small Bogomerom archipelago of islets in Lake Chad was formerly divided between Chad and Nigeria. The water level of Lake Chad has historically varied a lot, but this level has fallen so low that these islets are now part of the mainland of Africa.
Subnational divided islands 
There are islands that lie across different provinces or states of the same country. An example would be Killiniq Island of Canada, which is divided between Newfoundland and Labrador and Nunavut, whereas Melville Island and Victoria Island are divided between Nunavut and the Northwest Territories. In Australia, the Boundary Islet is divided between Tasmania and Victoria. Ellis Island, itself in the United States state of New Jersey, contains an exclave of the state of New York. Zhongshan Dao, in the People's Republic of China, is divided between Guangdong Province and the Special Administrative Region of Macau.
See also 
- Condominium (international law) - land jointly administered by two states, rather than divided between them (e. g., Pheasant Island, administered by France and Spain during alternating periods of six months).
- Category:Disputed islands and list of territorial disputes - includes many islands claimed by multiple countries, but administered by one.
- Guantanamo Bay Naval Base - leased indefinitely by the United States but with sovereignty retained by Cuba
- Korean Demilitarized Zone - includes several small islands
- List of islands in lakes
- Hans Island - April 2012 negotiations between Canada and Denmark on behalf of Greenland, not yet finalized, call for either a joint condominium or spliting the disputed island's sovereignty in half.
- "Islands by land area". UN system-wide Earthwatch. United Nations Environment Programme. 1998-02-18. Retrieved 2009-09-27.
- Margedant, Udo; Thomas Ellerbeck (1991). Politische Landeskunde Mecklenburg-Vorpommern (in German). Mecklenburg-Vorpommern: Landeszentrale für politische Bildung. p. 89.
- Map of Inakari, the Finnish part of Kataja
- "Border Station". King Fahd Causeway. King Fahd Causeway Authority. Retrieved 2009-09-27.
- Map of Koiluoto, the Finnish part of Koiluoto
- Jacques Boisvert. "Province Island". Retrieved 2006-11-04. "It is the largest island in Lake Memphremagog, being 77 acres, of which 7 acres, are in the United States."
- "Norway-Russia Boundary Map: Boundary markers 167–177: Sandneset-Klistervatn" (in Norwegian/Russian). Norwegian Boundary Commission for the Norway-Russia border. Retrieved 2007-09-25. — boundary markers #169-172
- "Norway-Russia Boundary Map: Boundary markers 7–14: Grenseberg-Ødevasselva" (in Norwegian/Russian). Norwegian Boundary Commission for the Norway-Russia border. Retrieved 2007-09-25. — boundary markers #12-13 (Korkeasaari) & #14 (unnamed islet) )
- Portion of Nuijamaanjärvi with Äikkäänniemi marked from Citizen's Mapsite of Finland.
- Portion of Yla-Tirja with divided islands at markers 93 (Suursaari) and 94 (smaller island) from Citizen's Mapsite of Finland.
- Portion of Melaselänjärvi showing Tarraassiinsaari and Härkäsaari from Citizen's Mapsite of Finland.
- Portion of Melaselänjärvi showing Kiteensaari from Citizen's Mapsite of Finland.
- Portion of Kokkojärvi showing Rajasaari from Citizen's Mapsite of Finland.
- Portion of Vuokkijärvi showing Kalmasaari from Citizen's Mapsite of Finland.
- Portion of Hietajärvi showing Varposaari from Citizen's Mapsite of Finland.
- Portion of Parvajärvi showing Parvajärvensaari from Citizen's Mapsite of Finland.
- Office of the Geographer, Bureau of Intelligence and Research (1967-02-01). International Boundary Study No. 74: Finland–U.S.S.R. boundary (PDF). United States Department of State. p. 21. "Hence the frontier runs...to a point on a small unnamed island in Lake Pukarinjarvi between the cape west of the village of Laitela and the Niittysaaryi island."
- Portion of Pukarijärvi with Keuhkosaari marked from Citizen's Mapsite of Finland.
- International Boundary Study No. 74, page 22. ""The frontier follows the creek down to Lake Onkamojarvi, intersects the small island of Siiheojansuusaai and proceeds in a straight line to the small island of Tossensaari."
- Portion of Onkamojärvi from Citizen's Mapsite of Finland (Siiheojansuusaari is IV/179; Tossonsaari is IV/180)
- Portion of Kivisarijärvi with divided island marked from Citizen's Mapsite of Finland.
- Neighborhood of boundary marker 347A, with divided island marked from Citizen's Mapsite of Finland.
- Verified at Norwegian state cartographic agency website (English) (Norwegian) (Sami)
- Søndre Boksjø:
- Salholmen: ; Trollön:
- Tannsjøen Island ("Nr 54" on Norwegian map):
- Kroksjøen's island:
- Vonsjøen's island:
- Skurdalssjøen's island:
- Gihcijoka island:
- Čoarvejávri's islands: largest:; middle: ; southern:
- Krogh, Jan S. "Lake Druksiai". Retrieved 2006-12-10. The international border is marked on the map.
- "World Lakes Database: LAKE DRUKSIAI". International lakes environment committee. Retrieved 2006-12-10. "Number of main islands (name and area): Zamok (0.26 km²), Sosnovec (0.048 km²), Utovec (0.0088 km²) and 5 nameless islands."
- "Bathymetric map of Lake Drūkšiai" (GIF). International lakes environment committee. Retrieved 2006-12-10.[dead link] Sosnovec is named on this map.
- Coordinates of Lake Drūkšiai:
- Verified against Ordnance Survey of Ireland 6-inch map of the townland of Tober, County Donegal; surveyed 1905-05-05. Coordinates: Irish national grid reference system: G996663
- Office of the Geographer, Bureau of Intelligence and Research (1976-02-20). International Boundary Study No. No. 154 – Djibouti – Ethiopia Boundary (PDF). United States Department of State. p. 8. "From Monument No. 53 on the south bank of Lake Abbe, the border crosses the lake from south to north continuing in a straight line for 30 kilometers. It cuts across the islet of hill 255 off Cape Aleilou."
- "Map of Commune of Schengen" (PDF). Commune of Schengen. Retrieved 2006-12-10.. Coordinates:
- Дополнительное соглашение между Российской Федерацией и Китайской Народной Республикой о российско-китайской государственной границе на ее Восточной части от 14 октября 2004 года.
- The northern shore of Corocoro is on the open ocean, but it is not truly a sea island as the southern boundary is a freshwater channel. The island is claimed in its entirety by Venezuela.
- Office of the Geographer, Bureau of Intelligence and Research (1985-04-15). International Boundary Study No. 174: Brazil - Colombia boundary (PDF). United States Department of State. p. 8. "The final report allocated all river islands on the basis of the thalweg with the exception of San Jose Island on the Rio Negro which was split between Brazil (southern half) and Colombia." Co-ordinates:
- Barros, Vicente (Coordinator) Impact Of Global Change On The Coastal Areas Of The Rio De La Plata: Sea Level Rise And Meteorological Effects. Page 7
- See map of Nawabganj District, map of Rajshahi District, and map of Daulatpur upazila of Kushtia District, all in Bangladesh.
- See map of Dilma upazila in Nilphamari District, Bangladesh.
- See map of Kurigram district, Bangladesh.
- Asiatic Society of Bangladesh. "Banglapedia: "Char"". Retrieved 2006-11-06.
- Office of the Geographer, Bureau of Intelligence and Research (1964-11-23). International Boundary Study No. 41: Greece - Turkey boundary (PDF). United States Department of State. p. 7. "Returning to the median of the Maritsa, [...] the boundary continues [...] to boundary marker No. 24 on the northern end of an island designated "Q". Thence, the boundary line extends a distance of 800.5 feet to marker No. 25 near the center, thence a distance of 1,804 feet to marker No. 26 on the southwestern extremity of island "Q"."
- Map highlighting the islet in the Uutuanjoki from the Citizen's Map Site of Finland
- Islet in the Vadet near Tunnsjø:
- Ramerini, Marco. "Dutch and Courlanders in Tobago: A history of the first settlements, 1628-1677". Retrieved 2007-10-01.
- Wolff, Sir Henry Drummond (1855). The island empire, or, Scenes of the first exile of the Emperor Napoleon I: together with a narrative of his residence on the island of Elba, taken from local information, the papers of the British resident, and other authentic sources. Bosworth. pp. 304–322. Retrieved 27 August 2011.
- Frey, Linda; Frey, Marsha (1995). The treaties of the War of the Spanish Succession: an historical and critical dictionary. Greenwood Publishing Group. pp. 421–2. ISBN 978-0-313-27884-6. Retrieved 27 August 2011.
- Office of the Geographer (June 1969). "Chad-Nigeria boundary" (JPEG). United States Department of State. Retrieved 2006-12-06.
- "April 11, 2012 audio report on Hans Island". =Canadian Broadcasting Corporation. Retrieved 2012-04-24.