Memnon was metropolitan bishop of Ephesus during the third ecumenical council.
Delays in the opening of the council were blamed by Nestorius on Memnon.
[2] Memnon hosted the second session of the Council in his episcopal palace and at the fourth session Cyril and Memnon presented a formal protest against John of Antioch for convening a separate conciliabulum, which condemned both of them.
[3] Reportedly out of jealousy, Memnon sought to get rid of Bassianus, a priest under him, by ordaining him to the bishopric of Evaza.
Bassianus refused the position and in 444 became, by an irregular process, Memnon's second successor.