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.
Notes on Muscovite Affairs
"Muscovy" in the 16th century was the Russian state which separated itself from the Kievan Rus' after it fell apart. It evolved into the Russian Empire under Peter the Great starting at the end of the 17th century. Russia was the region, Muscovy was the state until it no longer included just Moscow. Muscovy was then ruled by the Muscovite monarchy, starting with Ivan III (1462–1505), who expanded Muscovy, and ending with Ivan IV, who claimed the title "Tsar of Russia".