Zoe Palaiologina (Greek Ζωή Παλαιολόγου, Russian Софья Фоминична Палеолог, c. 1455 - April 7, 1503), Grand Duchess of Moscow, was a niece of the last Byzantine emperor Constantine XI and second wife of Ivan III of Russia.
Her father was Thomas Palaeologus, the Despot of Morea. Together with her brothers, she was taken to Rome after conquest of Morea by Mehmed II of the Ottoman Empire in 1460. In Rome, her Greek name Zoe was changed to Sophia. In 1469, Pope Paul II offered to marry her to the Russian monarch in order to unite the Orthodox and Catholic churches. The widowed Russian prince married unattractive and haughty Sophia at the Dormition Cathedral on November 12, 1472. The cardinal Johannes Bessarion, sent by the Pope to Moscow, however, did not succeed in his mission.
Over the years, Sophia started to wield great influence on her aged husband. It is thought that she was the first to introduce the Kremlin to grand Byzantine ceremonies and meticulous etiquette. The idea of Moscow as the Third Rome evidently pleased her. Shortly before her death she persuaded her husband to pass the throne to her son Vasili, rather than to Ivan's grandson Dmitry, as had been planned earlier. Apart from Vasili III, only her fifth son, Andrey of Staritsa, left issue.