Bosnia and Herzegovina contains 3.3 million people distributed across two constitutive entities and one district. The Federation of Bosnia and Herzegovina occupies 51 percent of territory, Republika Srpska holds 49 percent, and Brčko District exists as a self-governing unit under international supervision in the northeast. The 1995 Dayton Agreement established this structure, ending a war that killed approximately 100,000 people between 1992 and 1995. The Federation operates under a cantonal system with ten cantons, each possessing its own government and assembly. Republika Srpska functions as a single administrative unit with centralized governance from Banja Luka. Brčko District answers to neither entity, administered instead by its own democratic institutions under final sovereignty of the state.
Three recognized constituent peoples—Bosniaks, Serbs, and Croats—hold constitutional status alongside a category for Others. The 2013 census recorded 50.1 percent Bosniaks, 30.8 percent Serbs, and 15.4 percent Croats, though Republika Srpska authorities disputed methodology and results. Bosniaks concentrate in central Bosnia, Sarajevo, and portions of eastern Bosnia. Serbs form majorities across most of Republika Srpska and municipalities in northern and eastern regions. Croats dominate in western Herzegovina and select cantons in the Federation. The war displaced 2.2 million people, approximately half the prewar population. Many never returned. Sarajevo held 527,000 people in 1991 but dropped to 275,000 by 1996. The city now counts approximately 350,000 residents, substantially below prewar figures.
The Ottoman Empire controlled Bosnia from 1463 until 1878, a 415-year period that transformed demographic and religious composition. The empire conquered the medieval Bosnian Kingdom under King Stjepan Tomašević, executing him after a brief siege of Bobovac fortress in 1463. Ottoman administrators divided territory into sanjaks, with the Bosnia Eyalet eventually encompassing a region larger than present borders. Significant numbers of Slavic inhabitants converted to Islam during the first two centuries of Ottoman rule. The exact percentage remains disputed, but by the 17th century Muslims formed a plurality. Catholic and Orthodox Christians remained as protected dhimmi communities, paying additional taxes but retaining religious practice. The millet system organized subjects by religious affiliation rather than ethnicity, a structure that established religious identity as the primary social marker.
Austria-Hungary occupied Bosnia in 1878 following the Congress of Berlin, then formally annexed the territory in 1908. This annexation crisis heightened tensions with Serbia and Russia, contributing to the conditions preceding World War One. The occupation introduced rail lines, industrial development, and modernized urban infrastructure, particularly in Sarajevo and Mostar. On June 28, 1914, Gavrilo Princip assassinated Archduke Franz Ferdinand at Latin Bridge in Sarajevo, an event that triggered declarations of war across Europe within five weeks. Princip belonged to Young Bosnia, a South Slav nationalist organization supported by the Black Hand network operating from Serbia. He fired two shots at 10:45 local time from a position outside Moritz Schiller's delicatessen. Franz Ferdinand died within minutes, his wife Sophie within the hour.
The Kingdom of Serbs, Croats and Slovenes formed in 1918, renamed Yugoslavia in 1929. Bosnia became an internal region without republican status, divided among several banovinas under the 1929 reorganization. Muslims received no national recognition in the interwar kingdom, classified instead by Serbian or Croatian identity. World War Two brought occupation, partition, and massive civilian casualties. The Nazi-aligned Independent State of Croatia annexed most of Bosnia, implementing policies that killed hundreds of thousands of Serbs, Jews, Roma, and anti-fascist Croats. Chetniks, predominantly Serbian monarchist forces, committed massacres against Muslims and Croats. Partisan forces under Josip Broz Tito fought Axis powers and domestic rivals, ultimately gaining control by 1945. The 1943 session of the Anti-Fascist Council for the National Liberation of Yugoslavia in Jajce established Bosnia and Herzegovina as one of six constituent republics in postwar Yugoslavia.
Socialist Yugoslavia granted Bosnia and Herzegovina full republican status with borders roughly matching current territory. The 1948 census did not recognize Muslim as a national category, forcing citizens to declare as Serb, Croat, or undeclared. The 1961 census introduced "Muslim in the ethnic sense," and the 1971 census formalized Muslims as a constituent nation with capital M, indicating nationality rather than solely religion. This recognition responded to demands from Muslim intellectuals and politicians who argued their community constituted a distinct South Slav nation shaped by unique historical experience under Ottoman rule. Bosnia became Yugoslavia's most ethnically mixed republic, with no group holding a majority in the 1991 census. Sarajevo hosted the 1984 Winter Olympics, constructing venues on Mount Bjelašnica, Mount Igman, and Mount Jahorina that would later see combat.