It depends of country and time. Russia (after XVI century) and any countries in ancient world: King - Tsar (царь), Queen - Tsaritsa (царица). Western Europe (from medieval to modern times): King - Korol' (король), Queen - Koroleva (королева). Empire (any empire in the World, like Chinese, Roman, Aztec etc): Emperor - Imperator (император), Emperatress - Imperatritsa (императрица).

king: король - korol' (pronounced karOl) queen: королева - koroleva (pronounced karaliEva)

Russian king = царь (tsar') Russian queen=царица(tsaritsa) Russian prince=царевич(tsarevitch') Russian princess=царевна(tsarevna)

King - король (korol') Queen - королева (koroleva)