Tsar

Tsar is the Russian for the Roman Caesar.

By the 16th century, the Russian ruler had emerged as a powerful, autocratic sovereign. After Grand Duke Ivan III's marriage to Sophia Paleologue, Princess Sophia of Achaia, the niece of the last Emperor of the Byzantine Empire, he styled himself Tsar. The Moscow court now adopted Byzantine terms, rituals, titles, and emblems such as the double-headed eagle, which survives as the coat of arms of Russia.