Career
Already at a young age he became a monk and was soon after ordained a priest. Despite being a fervent anti-unionist, he was sent by the Byzantine emperor Manuel II Palaiologos (reigned 1391–1425) to participate in the discussions for a prospective union with Pope Urban VI (1378-1389). Eventually Euthymius advanced to the post of protosynkellos, after which he became Patriarch of Constantinople.
During his tenure, he endeavoured to remove the Church from imperial control and act autonomously.
Of his writings, only a philosophical treatise "On being and not being" and two letters survive. he died on 29 March 1416.