Siberia ( sy-BEER-ee-ə; Russian: Сибирь, romanized: Sibir', IPA: [sʲɪˈbʲirʲ] ), also known as Asian Russia, is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states since the lengthy conquest of Siberia, which began with the fall of the Khanate of Sibir in 1582 and concluded with the annexation of Chukotka in 1778. Siberia is vast and sparsely populated, covering an area of over 13.1 million square kilometres (5,100,000 sq mi) – about three-quarters of Russia's total area, but home to roughly a quarter of Russia's population. Novosibirsk, Krasnoyarsk, and Omsk are the largest cities in the area.
Because Siberia is a geographic and historic concept and not a political entity, there is no single precise definition of its territorial borders. Traditionally, Siberia spans the entire expanse of land from the Ural Mountains to the Pacific Ocean, with the Ural River usually forming the southernmost portion of its western boundary, and includes most of the drainage basin of the Arctic Ocean. It is further defined as stretching from the territories within the Arctic Circle in the north to the northern borders of Kazakhstan, Mongolia, and China in the south, although the hills of north-central Kazakhstan are also commonly included. The Russian government divides the region into three federal districts (groupings of Russian federal subjects), of which only the central one is officially referred to as "Siberian"; the other two are the Ural and Far Eastern federal districts, named for the Ural and Russian Far East regions that correspond respectively to the western and eastern thirds of Siberia in the broader sense.
