Niš, city in Serbia, on the River Nišava. It is an important railway junction with rail repair workshops, and also a leading industrial centre, producing leather goods, cigarettes, and armaments. Academic institutions include the University of Niš (1965).

The city, an important settlement in Roman times, was the birthplace of the Roman Emperor Constantine I. It fell in succession to the Huns, Bulgars, Hungarians, Byzantines, Serbs, and Ottoman Turks and was almost constantly in Turkish possession from the 15th century until it was retaken by the Serbs in 1878. Niš was a capital of Serbia until 1901. It was occupied by the Germans during World War II. Population 173,390 (2002).