Western Siberia or West Siberia (Russian: Западная Сибирь, romanized: Zapadnaya Sibir') is a part of the greater Siberia and mostly located in the Russian Federation. It lies between the region of Ural and the Yenisei River which conditionally divides Siberia into two halves.
The area of Western Siberia is 2,500,000 square kilometers (970,000 sq mi). Nearly 80% of Western Siberia is located within the West Siberian Plain. The largest rivers of the region are the Irtysh and the Ob.
Since the medieval times, the region was part of Golden Horde. After its dissolution in 15th century, on its territory was formed Khanate of Sibir centered in Tyumen. Since the late 16th century it has been part of bigger Russia after its conquest, while its southern regions became part of the Kazakh Khanate. The modern international borders in the region between Russia and Kazakhstan were formed in late 20th century with dissolution of the Soviet Union.
The most populous city of Western Siberia is the city of Novosibirsk. Other major cities include: