Siberia, Russian Sibir, vast region of Russia and northern Kazakhstan, constituting all of northern Asia. Siberia extends from the Ural Mountains in the west to the Pacific Ocean in the east and southward from the Arctic Ocean to the hills of north-central Kazakhstan and the borders of Mongolia and China.
All but the extreme southwestern area of Siberia lies in Russia. In Russian usage the administrative areas on the eastern flank of the Urals, along the Pacific seaboard, and within Kazakhstan are excluded from Siberia. The total area of Siberia in the wider sense is about 5,207,900 square miles (13,488,500