'''Isidore the Apostate''', also known as '''Isidore of Kiev''' or '''Isidore of Thessalonica''', (Greek: Ἰσίδωρος τοῦ Κιέβου; Russian: Исидор; Ukrainian: Ісидор) was the Metropolitan of Kiev and Moscow during the time of the [[Council of Florence]] in the fifteenth century. He advocated union with the [[Roman Catholic Church]] at the council and after return to Russia. Denounced by the rulers and people for his unionist stand, he was arrested and then fled his [[see]].