Russian Empire
Though the Empire was only officially proclaimed by Tsar Peter I following the Treaty of Nystad (1721), some historians would argue that it was truly born either when Ivan III of Russia conquered Veliky Novgorod in 1478, or when Ivan the Terrible conquered the Khanate of Kazan in 1552. According to another point of view, the term "Tsardom", which was used after the coronation of Ivan IV in 1547, was already a contemporary Russian word for empire.
Russia
Catherine II ("the Great"), who ruled in 1762–96, presided over the Age of Russian Enlightenment. She extended Russian political control over the Polish-Lithuanian Commonwealth and incorporated most of its territories into Russia during the Partitions of Poland, pushing the Russian frontier westward into Central Europe. In the south, after successful Russo-Turkish Wars against Ottoman Turkey, Catherine advanced Russia's boundary to the Black Sea, defeating the Crimean Khanate. As a result of victories over Qajar Iran through the Russo-Persian Wars, by the first half of the 19th century Russia also made significant territorial gains in Transcaucasia and the North Caucasus, forcing the former to irrevocably cede what is nowadays Georgia, Dagestan, Azerbaijan and Armenia to Russia. This continued with Alexander I's (1801–25) wresting of Finland from the weakened kingdom of Sweden in 1809 and of Bessarabia from the Ottomans in 1812. At the same time, Russians colonized Alaska and even founded settlements in California, such as Fort Ross.
In 1803–1806, the first Russian circumnavigation was made, later followed by other notable Russian sea exploration voyages. In 1820, a Russian expedition discovered the continent of Antarctica.