The Kingdom of Yugoslavia (Yugoslav,Cyrillic script: Краљевина Југославија; Latin script: Kraljevina Jugoslavija) was a state stretching from the Western Balkans to Central Europe which existed during the often-tumultuous interwar era of 1918–1941. It was formed in 1918 by the merger of the provisional State of Slovenes, Croats and Serbs, formed from territories of the defunct Austro-Hungarian Empire, with the formerly independent Kingdom of Serbia. The Kingdom of Montenegro united with Serbia just five days earlier, while the regions of Kosovo, Vojvodina and Vardar Macedonia were parts of Serbia prior to the unification. For its first eleven years of existence it was officially called Kingdom of Serbs, Croats and Slovenes, but the term Yugoslavia was its colloquial name from the very beginning.^{[citation needed]} On 17 April 1941, Yugoslavia was occupied by Nazi Germany and was reorganised into four provinces under foreign rule; a royal government-in-exile, recognized by the United Kingdom and later by all the Allied powers, was established in London. The Kingdom was succeeded by a provisional regime named Democratic Federal Yugoslavia established on 2 November 1944 by an agreement between the government of the Kingdom of Yugoslavia represented by Ivan Šubašić and the Yugoslav Partisans represented by Josip Broz Tito. Democratic Federal Yugoslavia was created following the successful conclusion of the agreement of cooperation decided by the Treaty of Vis signed by Šubašić and Tito at the behest of pressure by British Prime Minister Winston Churchill.

Yugoslavia (Croatian, Serbian, Slovene, Macedonian: Jugoslavija; Cyrillic: Југославија) was a country in the western part of the Balkans during most of the 20th century which was established three times under differing forms of government.

The first country to be known by this name was the Kingdom of Yugoslavia, which before 3 October 1929 was known as the Kingdom of Serbs, Croats and Slovenes. It was established on 1 December 1918 by the union of the State of Slovenes, Croats and Serbs and the Kingdom of Serbia (the Kingdom of Montenegro was annexed on 13 November 1918, and the Conference of Ambassadors in Paris gave international recognition to the union on 13 July 1922). The Kingdom of Yugoslavia was invaded by the Axis powers in 1941, and because of the events that followed, was officially abolished in 1943 and 1945.

The second country with this name was the Democratic Federal Yugoslavia, proclaimed in 1943 by the Yugoslav Partisans resistance movement during World War II. It was renamed to the Federal People's Republic of Yugoslavia in 1946, when a communist government was established. In 1963, it was renamed again to the Socialist Federal Republic of Yugoslavia (SFRY). This was the largest Yugoslav state, as Istria, Rijeka and Zadar were added to the new Yugoslavia after the end of World War II.