By the 16th century, the Russian ruler had emerged as a powerful, autocratic figure, a Tsar. By assuming that title, the sovereign of Moscow tried to emphasize that he was a major ruler or emperor on par with the Byzantine emperor or the Mongol khan. Indeed, after Ivan III's marriage to Sophia Palaiologina, the niece of Constantine XI Palaiologos, the Moscow court adopted Byzantine terms, rituals, titles, and emblems such as the double-headed eagle, which survives as the Coat of Arms of Russia.

At first, the Byzantine term autokrator expressed only the literal meaning of an independent ruler, but in the reign of Ivan IV (1533-1584) it came to mean unlimited rule. Ivan IV was crowned Tsar and thus was recognized, at least by the Russian Orthodox Church, as Emperor. Philotheus of Pskov claimed that after Constantinople fell to the Ottoman Empire in 1453, the Russian Tsar was the only legitimate Orthodox ruler, and that Moscow was the Third Rome because it was the final successor to Rome and Constantinople, the centers of Christianity in earlier periods. That concept was to resonate in the self-image of Russians in future centuries.