Siberia, the mainland part of Russia in Asia. Siberia is a geographic region rather than a political unit; it lies entirely within Russia. Because of their close association, geographic and economic ties, Sakhalin and the northern part of Kazakhstan are sometimes considered part of Siberia.
With an area of some 5,000,000 square miles (13,000,000 km 2), Siberia makes up about 75 per cent of the territory of Russia and is more than a third larger than the United States. It extends from the Ural Mountains to the Pacific Ocean (a distance of as much as 3,800 miles [6,100 km]) and from China and Mongolia northward to the Arctic Ocean (some 2,000 miles [3,200 km]).