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.
Early modern period
In development of the Third Rome ideas, the Grand Duke Ivan IV (the "Awesome" or "the Terrible") was officially crowned the first Tsar ("Caesar") of Russia in 1547. The Tsar promulgated a new code of laws (Sudebnik of 1550), established the first Russian feudal representative body (Zemsky Sobor) and introduced local self-management into the rural regions. During his long reign, Ivan IV nearly doubled the already large Russian territory by annexing the three Tatar khanates (parts of disintegrated Golden Horde): Kazan and Astrakhan along the Volga River, and Sibirean Khanate in South Western Siberia. Thus by the end of the 16th century Russia was transformed into a multiethnic, multiconfessional and transcontinental state.