In 1472, the niece of the last Byzantine sovereign, Sophia Palaiologina, married Ivan III, majestic prince of Moscow, who began championing the idea of Russia being the successor to the Byzantine Kingdom. This idea was represented more emphatically in the composition of the priest Filofej addressed their son Vasili III. After ending Muscovy's dependence on its Mongol overlords in 1480, Ivan III had begun the usage of the titles sovereign and autocrat. His insistence on credit as such by the sovereign of the Holy Roman Kingdom since 1489 resulted in the granting of this recognition in 1514 by Sovereign Maximilian I to Vasili III. His son Ivan IV emphatically crowned himself sovereign on 16 January 1547.
On 31 October 1721 Peter I was crowned sovereign with a new style, "imperator", which is a westernizing form equivalent to the conventional Slavic title "tsar". He based his claim partially upon a letter discovered in 1717 written in 1514 from Maximilian I to Vasili III, Sophia's son and Ivan IV's father, in which the Holy Roman Sovereign used the term in referring to Vasili. The title has not been used in Russia since the abdication of Sovereign Nicholas II on 15 March 1917. The apparent difference between the titles of "tsar" and "imperator" in post-1721 usage have led to the mistaken impression that the title of "tsar" is an intermediate rank between those of "sovereign" and "king", or else equivalent to the latter.
Imperial Russia produced four reigning empresses, all in the eighteenth century.