Sliven, city in eastern Bulgaria, capital of Sliven Province, at the southern foot of the Balkan Mountains. It is a manufacturing center with products that include textiles, glass, carpets, electrical equipment, wines, and food products. Because of its strategic position at the entrance of mountain passes, the site has been settled since Roman times. The town was under Turkish occupation from the 15th to 19th century. Population (1996 estimate) 107,267.