Siberia ( sy-BEER-ee-ə; Russian: Сибирь, romanized: Sibir', IPA: [sʲɪˈbʲirʲ] (listen)) 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 part of the sovereign territory of Russia and its various predecessor states since the centuries-long conquest of Siberia, which began with the fall of the Khanate of Sibir in the late 16th century 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), but home to only one-fifth of Russia's population. Novosibirsk, Omsk, and Chelyabinsk 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.

Siberia is known worldwide for its long, harsh winters, with a January average of −25 °C (−13 °F). Although it is geographically situated in Asia, Russian sovereignty and colonization since the 16th century have rendered the region culturally and ethnically European. Over 85% of its population are of European descent, chiefly Russian (comprising the Siberian sub-ethnic group), and Eastern Slavic cultural influences predominate throughout the region. Nevertheless, there exist sizable ethnic minorities of Asian lineage, including various Turkic communities—many of which, such as the Yakuts, Tuvans, Altais, and Khakas, are indigenous—along with the Mongolic Buryats, ethnic Koreans, and smaller groups of Samoyedic and Tungusic peoples (several of whom are classified as indigenous small-numbered peoples by the Russian government), among many others.