Orsk, city, southwestern Siberia Russia, at the confluence of the Ural and Or rivers. The city is the transportation and processing center of a region rich in minerals. It has plants processing iron and steel, nickel, aluminum, and petroleum. Manufactures also include food products and machinery. In 1735 the fortress of Orenburg was built here; it was relocated to its present site in 1743. In the 19th century Orsk was known for its cattle market; major industrialization began in the late 1930s. Population (1995) 338,323.
