The Bosnian War (Serbo-Croatian: Rat u Bosni i Hercegovini / Рат у Босни и Херцеговини) was an international armed conflict that took place in Bosnia and Herzegovina between 1992 and 1995. The war is commonly seen as having started on 6 April 1992, following a number of earlier violent incidents. The war ended on 14 December 1995 when the Dayton accords were signed. The main belligerents were the forces of the Republic of Bosnia and Herzegovina, the Republic of Herzeg-Bosnia, and the Republika Srpska, the latter two entities being proto-states led and supplied by Croatia and Serbia, respectively.

The war was part of the breakup of Yugoslavia. Following the Slovenian and Croatian secessions from the Socialist Federal Republic of Yugoslavia in 1991, the multi-ethnic Socialist Republic of Bosnia and Herzegovina – which was inhabited by mainly Muslim Bosniaks (44%), Orthodox Serbs (32.5%) and Catholic Croats (17%) – passed a referendum for independence on 29 February 1992. Political representatives of the Bosnian Serbs boycotted the referendum, and rejected its outcome. Anticipating the outcome of the referendum, the Assembly of the Serb People in Bosnia and Herzegovina adopted the Constitution of the Serbian Republic of Bosnia and Herzegovina on 28 February 1992. Following Bosnia and Herzegovina's declaration of independence (which gained international recognition) and following the withdrawal of Alija Izetbegović from the previously signed Cutileiro Plan (which proposed a division of Bosnia into ethnic cantons), the Bosnian Serbs, led by Radovan Karadžić and supported by the government of Slobodan Milošević and the Yugoslav People's Army (JNA), mobilised their forces inside Bosnia and Herzegovina in order to secure ethnic Serb territory. The war soon spread across the country, accompanied by ethnic cleansing.

The conflict was initially between Yugoslav Army units in Bosnia which later transformed into the Army of Republika Srpska (VRS) on the one side, and the Army of the Republic of Bosnia and Herzegovina (ARBiH), largely composed of Bosniaks, and the Croat forces in the Croatian Defence Council (HVO) on the other side. Tensions between Croats and Bosniaks increased throughout late 1992, resulting in the escalation of the Croat–Bosniak War in early 1993. The Bosnian War was characterised by bitter fighting, indiscriminate shelling of cities and towns, ethnic cleansing, and systematic mass rape, mainly perpetrated by Serb, and to a lesser extent, Croat and Bosniak forces. Events such as the siege of Sarajevo and the Srebrenica massacre later became iconic of the conflict.

The Serbs, although initially militarily superior due to the weapons and resources provided by the JNA, eventually lost momentum as the Bosniaks and Croats allied against the Republika Srpska in 1994 with the creation of the Federation of Bosnia and Herzegovina following the Washington agreement. Pakistan ignored the UN's ban on supply of arms, and airlifted anti-tank missiles to the Bosnian Muslims, while after the Srebrenica and Markale massacres, NATO intervened in 1995 with Operation Deliberate Force targeting the positions of the Army of the Republika Srpska, which proved key in ending the war. The war ended after the signing of the General Framework Agreement for Peace in Bosnia and Herzegovina in Paris on 14 December 1995. Peace negotiations were held in Dayton, Ohio, and were finalised on 21 November 1995.

By early 2008, the International Criminal Tribunal for the former Yugoslavia convicted forty-five Serbs, twelve Croats, and four Bosniaks of war crimes in connection with the war in Bosnia. Estimates suggest over 100,000 people were killed during the war. Over 2.2 million people were displaced, making it, at the time, the most violent conflict in Europe since the end of World War II. In addition, an estimated 12,000–50,000 women were raped, mainly carried out by Serb forces, with most of the victims being Bosniak women.