MENNON, bishop of EPHESUS. — He lived between the end of the 4th century and the first half of the 5th; he was already bishop of that Church in 431, when the great Council was convened.
During its proceedings he energetically supported St. Cyril of Alexandria (v.) against the partisans of Nestorius; but from the outset he had forbidden them the use of the churches and denied them permission to celebrate the feast of Pentecost there.
At the Council of the Orientals he was deposed together with Cyril and imprisoned, but was soon freed by order of the Emperor Theodosius and left in his see. One of his letters to the Constantinopolitan clergy is preserved.
BIBL.: Tillemont, XIV, pp. 295–485; Hefele-Leclercq, II, pp. 234–48; M. Jugie, Le decret d'Ephène sur les formules de foi et la politique anticatholique en Orient, in Echos d'Orient, 30 (1931), pp. 257–70; C. Hole, s. V. in Dictionary of Christian biography, III, p. 901 ff. Emanuele Romanelli