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 succeeded by the Soviet Union. It was one of the largest empires in world history, 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 of the world at the time, after Qing China and the British Empire. Like all empires, it represented a large disparity in economic, ethnic and religious positions. Its government, ruled by the Emperor, was the last absolute monarchy in Europe at the time of its demise.

Russia ⁱ/ˈrʌʃə/ or /ˈrʊʃə/ (Russian: Россия, tr. Rossiya; IPA: [rɐˈsʲijə] ( listen)), also officially known as the Russian Federation (Russian: Российская Федерация, tr. Rossiyskaya Federatsiya; IPA: [rɐˈsʲijskəjə fʲɪdʲɪˈratsɨjə] ( listen)), is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects. From northwest to southeast, Russia shares borders with Norway, Finland, Estonia, Latvia, Lithuania and Poland (both via Kaliningrad Oblast), Belarus, Ukraine, Georgia, Azerbaijan, Kazakhstan, China, Mongolia, and North Korea. It also has maritime borders with Japan by the Sea of Okhotsk, and the US state of Alaska by the Bering Strait. At 17,075,400 square kilometres (6,592,800 sq mi), Russia is the largest country in the world, covering more than one eighth of the Earth's inhabited land area. Russia is also the eighth most populous nation with 143 million people. It extends across the whole of northern Asia and 40% of Europe, spanning nine time zones and incorporating a wide range of environments and landforms. Russia has the world's largest reserves of mineral and energy resources and is the largest producer of oil and natural gas globally. Russia has the world's largest forest reserves and its lakes contain approximately one-quarter of the world's fresh water.

World War I (WWI), which was predominantly called the World War or the Great War from its occurrence until 1939 (World War II), and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918. It involved all the world's great powers, which were assembled in two opposing alliances: the Allies (based on the Triple Entente of the United Kingdom, France and Russia) and the Central Powers (originally centred around the Triple Alliance of Germany, Austria-Hungary and Italy; but, as Austria–Hungary had taken the offensive against the agreement, Italy did not enter into the war). These alliances both reorganised (Italy fought for the Allies), and expanded as more nations entered the war. Ultimately more than 70 million military personnel, including 60 million Europeans, were mobilised in one of the largest wars in history. More than 9 million combatants were killed, largely because of enormous increases in lethality of weapons, thanks to new technology, without corresponding improvements in protection or mobility. It was the sixth-deadliest conflict in world history, subsequently paving the way for various political changes such as revolutions in the nations involved.