Euthymius II of Constantinople

Euthymius II (Εὐθύμιος Β΄; died 29 March 1416) was patriarch of Constantinople from 1410 to 1416.

He became a monk at a young age and was soon after ordained a priest. He distinguished himself for his theological and rhetorical abilities, which he employed in defence of Palamism and against the Union of the Eastern Orthodox Church with the Roman Catholic Church, for which he was accorded the honorific appellation "Doctor of the Church". Despite being a fervent anti-unionist, he was sent by the Byzantine emperor Manuel II Palaiologos to participate in the discussions for a prospective union with Pope Urban VI. The mission achieved some success, but with no firm commitments on either side, and on his return to Constantinople he was promoted to archimandrite and became abbot of the prestigious Stoudios Monastery.

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. Euthymius II died on 29 March 1416.