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