Isidore of Kiev, also known as Isidore of Thessalonica (Greek: Ἰσίδωρος τοῦ Κιέβου; Russian: Исидор; Ukrainian: Ісидор; b. Thessalonica, 1385-d.Rome, 27 April 1463) was a Greek Metropolitan of Kiev, cardinal, humanist, and theologian. He was one of the chief Eastern defenders of reunion at the time of the Council of Florence,.