Memnon was metropolitan bishop of Ephesus during the third ecumenical council.[1]
At the Council he was a supporter of Cyril of Alexandria. 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.[4]