Yugoslavia (; Serbo-Croatian: Jugoslavija / [juslaija]; Slovene: Jugoslavija [juslija]; Macedonian: [jusavija]; lit.'South Slavic Land') was a country in Southeast Europe and Central Europe for most of the 20th century. It came into existence after World War I in 1918 under the name of the Kingdom of Serbs, Croats and Slovenes by the merger of the provisional State of Slovenes, Croats and Serbs (which was formed from territories of the former Austro-Hungarian Empire) with the Kingdom of Serbia, and constituted the first union of the South Slavic people as a sovereign state, following centuries in which the region had been part of the Ottoman Empire and Austria-Hungary. Peter I of Serbia was its first sovereign. The kingdom gained international recognition on 13 July 1922 at the Conference of Ambassadors in Paris. The official name of the state was changed to Kingdom of Yugoslavia on 3 October 1929.

Yugoslavia was invaded by the Axis powers on 6 April 1941. In 1943, a Democratic Federal Yugoslavia was proclaimed by the Partisan resistance. In 1944 King Peter II, then living in exile, recognised it as the legitimate government. The monarchy was subsequently abolished in November 1945. Yugoslavia was renamed the Federal People's Republic of Yugoslavia in 1945, when a communist government was established. It acquired the territories of Istria, Rijeka, and Zadar from Italy. Partisan leader Josip Broz Tito ruled the country as president until his death in 1980. In 1963, the country was renamed again, as the Socialist Federal Republic of Yugoslavia (SFRY).

The six constituent republics that made up the SFRY were the SR Bosnia and Herzegovina, SR Croatia, SR Macedonia, SR Montenegro, SR Serbia, and SR Slovenia. Serbia contained two Socialist Autonomous Provinces, Vojvodina and Kosovo, which after 1974 were largely equal to the other members of the federation. After an economic and political crisis in the 1980s and the rise of nationalism, Yugoslavia broke up along its republics' borders, at first into five countries, leading to the Yugoslav Wars. From 1993 to 2017, the International Criminal Tribunal for the former Yugoslavia tried political and military leaders from the former Yugoslavia for war crimes, genocide, and other crimes committed during those wars.

After the breakup, the republics of Montenegro and Serbia formed a reduced federative state, the Federal Republic of Yugoslavia (FRY), known from 2003 to 2006 as Serbia and Montenegro. This state aspired to the status of sole legal successor to the SFRY, but those claims were opposed by the other former republics. Eventually, it accepted the opinion of the Badinter Arbitration Committee about shared succession and in 2003 its official name was changed to Serbia and Montenegro. This state dissolved when Montenegro and Serbia each became independent states in 2006, with Kosovo having an ongoing dispute over its declaration of independence in 2008.

Croatia ( (listen), kroh-AY-shə; Croatian: Hrvatska, pronounced [xř̩ʋaːtskaː]), officially the Republic of Croatia (Croatian: Republika Hrvatska, (listen)), is a country at the crossroads of Central and Southeast Europe. It shares a coastline along the Adriatic Sea, and borders Slovenia to the northwest, Hungary to the northeast, Serbia to the east, Bosnia and Herzegovina and Montenegro to the southeast, and shares a maritime border with Italy to the west and southwest. Croatia's capital and largest city, Zagreb, forms one of the country's primary subdivisions, with twenty counties. The country spans an area of 56,594 square kilometres (21,851 square miles), with a population of nearly 3.9 million.

The Croats arrived in the 6th century and organised the territory into two duchies by the 9th century. Croatia was first internationally recognised as independent on 7 June 879 during the reign of Duke Branimir. Tomislav became the first king by 925, elevating Croatia to the status of a kingdom. During the succession crisis after the Trpimirović dynasty ended, Croatia entered a personal union with Hungary in 1102. In 1527, faced with Ottoman conquest, the Croatian Parliament elected Ferdinand I of Austria to the Croatian throne. In October 1918, the State of Slovenes, Croats and Serbs, independent from Austria-Hungary, was proclaimed in Zagreb, and in December 1918, merged into the Kingdom of Yugoslavia. Following the Axis invasion of Yugoslavia in April 1941, most of Croatia was incorporated into a Nazi installed puppet state, the Independent State of Croatia, which committed genocide against Serbs, Jews, and Roma. A resistance movement led to the creation of the Socialist Republic of Croatia, which after the war became a founding member and constituent of the Socialist Federal Republic of Yugoslavia. On 25 June 1991, Croatia declared independence, and the War of Independence was fought for four years following the declaration.

A sovereign state, Croatia is a republic governed under a parliamentary system. It is a member of the European Union, the United Nations, the Council of Europe, NATO, the World Trade Organization, and a founding member of the Union for the Mediterranean. An active participant in United Nations peacekeeping, Croatia has contributed troops to the International Security Assistance Force and took a nonpermanent seat on the United Nations Security Council for the 2008–2009 term. Since 2000, the Croatian government has invested in infrastructure, especially transport routes and facilities along the Pan-European corridors.

Croatia is classified by the World Bank as a high-income economy and ranks very high on the Human Development Index. Service, industrial sectors, and agriculture dominate the economy, respectively. Tourism is a significant source of revenue, with Croatia ranked among the 20 most popular tourist destinations. The state controls a part of the economy, with substantial government expenditure. The European Union is Croatia's most important trading partner. Croatia provides social security, universal health care, and tuition-free primary and secondary education while supporting culture through public institutions and corporate investments in media and publishing.