MARCO, bishop of ARETUSA. - A follower of Arius, he took part in the Council of Antioch in 341, and in the following year was a member of the delegation that went to Trier to Constans.
In 343 he was with the Eastern faction assembled at Philippopolis, after abandoning the Council of Sardica, and he also took part in the Synod of 351 against Photinus. In 359 he drew up the Homoian formula approved at the Council of Rimini, and subsequently participated in the Council of Seleucia. During the pagan restoration under Julian the Apostate, he was subjected to atrocious torments by his fellow citizens because he had destroyed a temple. He was still alive in 363, but must have died shortly afterwards.
St Gregory Nazianzen and Theodoret praise him for his zeal for religion, extol his wisdom and piety, and declare him to be full of every virtue. The Greek Church honours him as a martyr and commemorates him on 28 March.