Mennas or Menas, a Christian saint was appointed by the Byzantine emperor Justinian I as patriarch of Constantinople in the 536 The Pope Agapetus consecrated him to succeed Bishop Anthimus, who was a monophysite. He took positions against Origen. He was excommunicated in 547 and in 551 for taking positions counter to those held by the Pope. However, in both cases the sentence of excommunication was lifted quickly. The patriarchy of Mennas represents the greatest extent of papal influence in Constantinople.

His feast day in the Roman Catholic Church is August 25.