451), Syrian ecclesiastic, patriarch of Constantinople from 428 to 431, was a native of Germanicia at the foot of Mount Taurus, in Syria.
As monk in the neighbouring monastery of Euprepius, and afterwards as presbyter, he became celebrated in the diocese for his asceticism, his orthodoxy and his eloquence; hostile critics, such as the church historian Socrates, allege that his arrogance and vanity were hardly less conspicuous.
On the death of Sisinnius, patriarch of Constantinople (December 427), Theodosius perplexed by the various claims of the local clergy, appointed the disinguished preacher of Antioch to the vacant see.
Sisinnius, the successor of Atticus, consecrated him bishop of Cyzicus but the people there refused to receive him, and he remained at Constantinople.
On the death of Sisinnius, the famous Nestorius succeeded, and early in 429, on a festival of Virgin Mary, Proclus preached the celebrated sermon on the Incarnation inserted in the beginning of the Acts of the council of Ephesus.
In 438 he transported to Constantinople from Comana, and interred with great honour in the church of the Apostles, the remains of his old master Saint John Chrysostom, and thereby reconciled to the church his adherents who had separated in consequence of his condemnation.