The Yugoslav Wars were a series of separate but related ethnic conflicts, wars of independence and insurgencies that took place from 1991 to 2001 in what had been the Socialist Federal Republic of Yugoslavia (SFR Yugoslavia). The conflicts both led up to and resulted from the breakup of Yugoslavia, which began in mid-1991, into six independent countries matching the six entities known as republics that had previously constituted Yugoslavia: Slovenia, Croatia, Bosnia and Herzegovina, Montenegro, Serbia, and Macedonia (now called North Macedonia). SFR Yugoslavia's constituent republics declared independence due to rising nationalism. Unresolved tensions between ethnic minorities in the new countries led to the wars. While most of the conflicts ended through peace accords that involved full international recognition of new states, they resulted in a massive number of deaths as well as severe economic damage to the region.

During the initial stages of the breakup of Yugoslavia, the Yugoslav People's Army (JNA) sought to preserve the unity of the Yugoslav nation by eradicating all nationalists in the governments of the republics. However, it increasingly came under the influence of Slobodan Milošević, whose government invoked Serbian nationalism as an ideological replacement for the weakening communist system. As a result, the JNA began to lose Slovenes, Croats, Kosovar Albanians, Bosniaks, and Macedonians, and effectively became a fighting force of only Serbs and Montenegrins. According to a 1994 report by the United Nations (UN), the Serb side did not aim to restore Yugoslavia; instead, it aimed to create a "Greater Serbia" from parts of Croatia and Bosnia. Other irredentist movements have also been brought into connection with the Yugoslav Wars, such as "Greater Albania" (from Kosovo, idea abandoned following international diplomacy) and "Greater Croatia" (from parts of Herzegovina, abandoned in 1994 with the Washington Agreement).

Often described as one of Europe's deadliest armed conflicts since World War II, the Yugoslav Wars were marked by many war crimes, including genocide, crimes against humanity, ethnic cleansing, massacres, and mass wartime rape. The Bosnian genocide was the first European wartime event to be formally classified as genocidal in character since the military campaigns of Nazi Germany, and many of the key individuals who perpetrated it were subsequently charged with war crimes; the International Criminal Tribunal for the former Yugoslavia (ICTY) was established by the UN in The Hague, Netherlands, to prosecute all individuals who had committed war crimes during the conflicts. According to the International Center for Transitional Justice, the Yugoslav Wars resulted in the deaths of 140,000 people, while the Humanitarian Law Center estimates at least 130,000 casualties. Over their decade-long duration, the conflicts resulted in major refugee and humanitarian crises.

The Yugoslav Wars have alternatively been referred to as:

The state of Yugoslavia was created in the aftermath of World War I, and its population was mostly composed of South Slavic Christians, though the nation also had a substantial Muslim minority. Clear ethnic conflict between the Yugoslav peoples only became prominent in the 20th century, beginning with tensions over the constitution of the Kingdom of Serbs, Croats, and Slovenes in the early 1920s and escalating into violence between Serbs and Croats in the late 1920s after the assassination of Croatian politician Stjepan Radić. This nation lasted from 1918 to 1941, when it was invaded by the Axis powers during World War II, which provided support to the Croatian fascist Ustaše (founded in 1929), whose regime carried out the genocide of Serbs, Jews and Roma by executing people in concentration camps and committing other systematic and mass crimes inside its territory.

The predominantly Serb Chetniks, a Yugoslav Royalist and Serbian nationalist movement and guerrilla force, committed mass crimes against Muslims and Croats that are considered a genocide by several authors, and they also supported the instatement of a Serbian monarchy and the establishment of a Yugoslav federation. The Communist-led Yugoslav Partisans were able to appeal to all groups, including Serbs, Croats, and Bosniaks, and also engaged in mass killings. In 1945, the Federal People's Republic of Yugoslavia (FPRY) was established under Josip Broz Tito, who maintained a strongly authoritarian leadership that suppressed nationalism.

After Tito's death in 1980, relations between the six republics of the federation deteriorated. Slovenia, Croatia and Kosovo desired greater autonomy within the Yugoslav confederation, while Serbia sought to strengthen federal authority. As it became clear that there was no solution that was agreeable to all parties, Slovenia and Croatia moved towards independence. Although tensions in Yugoslavia had been mounting since the early 1980s, events in 1990 proved to be decisive. In the midst of economic hardship and the fall of communism in eastern Europe in 1989, Yugoslavia was facing rising nationalism among its various ethnic groups. By the early 1990s, there was no effective authority at the federal level. The Federal Presidency consisted of the representatives of the six republics, two provinces and the Yugoslav People's Army, and the communist leadership was divided along national lines.

The representatives of Vojvodina, Kosovo and Montenegro were replaced with loyalists of the president of Serbia, Slobodan Milošević. Serbia secured four out of eight federal presidency votes and was able to heavily influence decision-making at the federal level, since all the other Yugoslav republics only had one vote. While Slovenia and Croatia wanted to allow a multi-party system, Serbia, led by Milošević, demanded an even more centralized federation and Serbia's dominant role in it.