Strategically situated athwart land and river routes between Central Europe and the Balkans, Belgrade has been the target of numerous conquerors throughout history. The city grew around fortresses built by the Celts (3d cent. b.c.), Illyrians, and Romans. Under the name of Singidinum it served as the harbor for much of Rome's Danubian fleet. Captured by the Huns, Goths, Sarmathians, and Gepids, who destroyed its forts, the city was retaken by the Byzantine emperor Justinian in the 6th cent. a.d. It was held in the late 8th cent. by the Franks and from the 9th to 11th cent. by the Bulgars, who refortified it and named it Beligrad ("white fortress"). It was then ruled again by Byzantium before becoming the capital of Serbia in the 12th cent. Before it fell to the Ottoman sultan Sulayman I in 1521, it was under Hungarian control.

The Ottoman Turks made Belgrade their chief strategic fortress in Europe. Although the Austrians stormed it in 1688, 1717, and 1789, they were able to hold onto it only from the Treaty of Passarowitz (1718) until the Treaty of Belgrade (1739). Liberated by Karageorge and Miloš Obrenović during the Serbian uprising of 1806, Belgrade was recaptured by the Turks in 1813. The Turks largely left Serbia in 1815 but kept a garrison in the Belgrade fortress until 1867.

Belgrade became the capital of the Kingdom of Serbia in 1882. Occupied by Austrian troops during World War I, the city was made the capital of the new Kingdom of the Serbs, Croats, and Slovenes (Yugoslavia from 1929) after the war. During World War II, Belgrade suffered much damage and extreme hardship under the German occupation. It was liberated by Yugoslav partisans, with Soviet aid, in 1944. After the disintegration of the Yugoslav federation in the early 1990s, Belgrade remained the capital of a much smaller Yugoslavia, consisting of Serbia and Montenegro only, until that nation was reconstituted (2003-6) as Serbia and Montenegro. The city was a target of NATO bombers during the Kosovo crisis (1999).

Belgrade is noted for its fine parks, palaces, museums, and churches. The former Kalemegdan citadel is now a military museum. The 16th-century Barjak Mosque was built by Sulayman I. The city is the home of the Serbian Academy of Sciences, a university (founded 1863), a Roman Catholic archbishop, and an Orthodox Eastern patriarch.