The Russian Empire (Pre-reform Russian orthography: Россійская Имперія, Modern Russian: Российская Империя, translit: Rossiyskaya Imperiya) was a state that existed from 1721 until the Russian Revolution of 1917. It was the successor to the Tsardom of Russia and the predecessor of the short-lived Russian Republic, which was in turn succeeded by the Soviet Union. One of the largest empires in world history, the Russian Empire was surpassed in landmass only by the British and Mongol empires. At one point in 1866 it stretched from eastern Europe across Asia and into North America.
At the beginning of the 19th century, the Russian Empire extended from the Arctic Ocean in the north to the Black Sea on the south, from the Baltic Sea on the west to the Pacific Ocean and into North America on the east. With 125.6 million subjects registered by the 1897 census, it had the third largest population in the world at the time, after Qing China and the British Empire. Like all empires, it represented a large disparity in terms of economics, ethnicity and religion. Its government, ruled by an Emperor, was an absolute monarchy until the Revolution of 1905. Afterwards it became a constitutional monarchy, though its Emperor continued to wield considerable power during the new political regime until the final demise of the empire during the February Revolution of 1917, the result of strains brought about by participation in World War I.