A unilateral declaration of independence (UDI) or "unilateral secession" is a formal process leading to the establishment of a new state by a subnational entity which declares itself independent and sovereign without a formal agreement with the state from which it is seceding. The term was first used when Rhodesia declared independence in 1965 from the United Kingdom (UK) without an agreement with the UK.

Examples

Prominent examples of a unilateral declaration of independence other than Rhodesia's UDI in 1965 include that of the United States in 1776, the Irish Declaration of Independence of 1919 by a revolutionary parliament, Katanga's declaration of independence by Moise Tshombe in July 1960, the attempted secession of Biafra from Nigeria in 1967, the Proclamation of Bangladeshi Independence from Pakistan in 1970, the secession of the Turkish Republic of Northern Cyprus from Cyprus in 1983, the Palestinian Declaration of Independence from the Palestinian territories in 1988, and that of the Republic of Kosovo in 2008. During the Dissolution of the Soviet Union throughout 1991, many of its republics declared their independence unilaterally without agreement and were thus not recognised as legitimate by the Soviet Central Government.

During the breakup of Yugoslavia, the government of the United States asked the governments of Croatia and Slovenia to drop their UDI plans because of the threat of major war erupting in the Balkans because of it, and threatened that it would oppose both countries' UDIs on the basis of the Helsinki Final Act if they did so. However, four days later both Slovenia and Croatia announced their UDIs from Yugoslavia.

DateDeclared stateParent stateInternational recognitionNotes
1776United StatesGreat BritainYes
1777VermontGreat BritainNoVermont signed a separate armistice with Britain in 1781 before the surrender of Cornwallis at Yorktown. Effective retroactive recognition by the United States was granted in 1791 when Vermont became the 14th state.
1813CundinamarcaSpainNoNo other nation besides Venezuela, itself an unrecognised government at the time, recognised the independence of Cundinamarca. The nation was later incorporated by military force into the United Provinces of New Granada in 1814.
1813New GranadaSpainNoNo other nation besides Venezuela, itself an unrecognised government at the time, recognised the independence of New Granada. The nation would later join together with Venezuela to form the Republic of Colombia.
1816Río de la PlataSpainYes, after the military victoryDivision and dismembering of the independent country. Paraguay secession. Brazil invaded Uruguay. Spain recognized Argentine Independence in 1859.
1819Gran ColombiaSpainYesInitially recognised by the United States (1822), the United Kingdom (1825), the Netherlands (1829) and various other Hispanic American nations between 1822 and 1831. Recognised by Spain in 1881.
1821GreeceOttoman EmpireYesIntervention by France, Russia, and the United Kingdom in favour of Greece in the Greek War of Independence secured its independence in 1832.
1830BelgiumUnited NetherlandsYesUDI (4 October 1830) recognized by the major European powers following the London Conference of 20 December 1830.
1860-1861Confederate StatesUnited StatesNoConquered by United States
1898PhilippinesSpanish Empire SpainNoConquered by United States; became independent in 1946 by the Treaty of Manila.
1903PanamaColombiaYes
1905NorwaySwedenYes
1912AlbaniaOttoman EmpireYes
1917FinlandRussiaYesRecognized after victory in the Finnish War of Independence
1918EstoniaRussiaYesRecognized after victory in the Estonian War of Independence
1918LatviaRussiaYesRecognized after victory in the Latvian War of Independence
1918LithuaniaRussiaYesRecognized after victory in the Lithuanian Wars of Independence
1919Irish RepublicUnited KingdomNoBecame the Irish Free State upon the ratification of the Anglo-Irish Treaty.
1920KareliaSoviet RussiaNo
1921Baranya–BajaHungaryNo
1921MirditaAlbaniaPartialRecognized only by Greece
1922Kingdom of EgyptUnited KingdomYesUnilateral grant of independence by the British government
1931JiangxiChinaNo
1931CataloniaSpainNoSpanish sovereignty remained unchanged
1938Carpatho-UkraineCzechoslovakiaNo
1941UkraineSoviet UnionNo
1945IndonesiaNetherlandsYes
1960KatangaCongo-LéopoldvilleNoBreakaway Congolese province, secession forcibly ended by the United Nations Operation in the Congo in 1963.
1965RhodesiaUnited KingdomNoSelf-governing British colony, unilaterally declared itself independent as Rhodesia in 1965, renamed Zimbabwe Rhodesia and returned to British control in 1979, then gained international recognition as Zimbabwe in 1980.
1967AnguillaUnited KingdomNoReturned as a British Crown Colony in 1969.
1967BiafraNigeriaPartialRecognized by five countries. Present-day Nigeria
1971BangladeshPakistanYes
1971West PapuaIndonesiaNo
1973Guinea-BissauPortugalYes
1975North SolomonsAustraliaNoPresent-day Autonomous Region of Bougainville, Papua New Guinea
1975CabindaPortugalNoPresent-day Angola
1975East TimorPortugalNoShortly following the declaration of independence, the territory was invaded and annexed by Indonesia. A referendum in 1999 led to eventual independence in 2002.
1983Northern CyprusCyprusPartialStill claimed by Cyprus, and recognized as such by all UN member-states except for Turkey, which recognizes Northern Cyprus instead.
1988PalestineIsraelPartialClaims territories occupied by Israel since 1967 Israeli–Palestinian conflict and peace process still ongoing See: International recognition of the State of Palestine
1988West PapuaIndonesiaNo
1990LatviaSoviet UnionYesAfter the failed 1991 Soviet coup attempt, the Soviet Union recognized Latvia's independence.
1990LithuaniaSoviet UnionYesAfter the failed 1991 Soviet coup attempt, the Soviet Union recognized Lithuania's independence.
1990NamibiaSouth AfricaYes
1990KarakalpakstanUzbekistanNoIncorporated into Uzbekistan in 1993.
1991EstoniaSoviet UnionYes
1991SomalilandSomaliaNoStill claimed by Somalia
1991CroatiaYugoslaviaYesSet off Croatian War of Independence
1991SloveniaYugoslaviaYesSet off Ten-Day War
1991IchkeriaSoviet UnionPartialPresent-day Chechnya, part of Russia. Retroactively recognized by Ukraine in 2022
1991TransnistriaMoldovaPartialStill claimed by Moldova, recognized by 2 partially unrecognised breakaway states South Ossetia and Abkhazia (+ the former Nagorno-Karabakh Republic).
1991Nagorno-KarabakhAzerbaijanNoRecognized by 3 partially unrecognised breakaway states South Ossetia, Abkhazia and Transnistria between 1991 and 2023. Incorporated back into Azerbaijan as aftermath of Second Nagorno-Karabakh War and 2023 Azerbaijani offensive in Nagorno-Karabakh.
1991South OssetiaGeorgiaPartialStill claimed by Georgia. Recognized by 5 UN member-states.
1992Bosnia and HerzegovinaYugoslaviaYesSet off Bosnian War
1999AbkhaziaGeorgiaPartialStill claimed by Georgia. Recognized by 5 UN member-states.
2008KosovoSerbiaPartialStill claimed by Serbia A United Nations General Assembly (UNGA) resolution adopted on 8 October 2008 backed the request of Serbia to seek an International Court of Justice advisory opinion on Kosovo's declaration of independence. On 22 July 2010, the ICJ ruled that the declaration of independence of Kosovo "did not violate any applicable rule of international law", because its authors, who were "representatives of the people of Kosovo", were not bound by the Constitutional Framework (promulgated by UNMIK) or by UNSCR 1244 that is addressed only to United Nations member states and organs of the United Nations. See: International recognition of Kosovo
2014CrimeaUkrainePartialAnnexed by Russia; still claimed by Ukraine. Recognized only by 7 UN member states.
2014Donetsk LuhanskUkrainePartialAnnexed by Russia; still claimed by Ukraine. Recognized only by 8 UN member states.
2017CataloniaSpainNoSpanish sovereignty remained unchanged

Legal aspects

The International Court of Justice, in a 2010 advisory opinion, declared that unilateral declarations of independence were not illegal under international law.

See also