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.
Tsardom of Russia
The Tsardom of Russia (, "Russkoje tsarstvo" later changed to , "Rossiyskoye tsarstvo"), Polish-Lithuanian Commonwealth called it Tsardom of Muscovy, was the centralized Russian state from the assumption of the title of Tsar by Ivan IV in 1547 until the foundation of the Russian Empire by Peter the Great in 1721.