Peter Mongus a Monophysite, flourished as patriarch of Alexandria in the 5th century. Liberatus gives him also the surname of the Stammerer. He was ordained deacon by Dioscorus, successor of Cyril, who held the patriarchate for seven years (A.D. 444-451). Peter was the ready participator in the violences of Dioscorus, and earnestly embraced his cause when he was deposed by the Council of Chalcedon, withdrawing from the communion of the successor of Dioscorus, Proterius, who supported the cause of the council, and uniting in the opposition raised by Timothy LElurus and others. Peter was consequently sentenced, apparently by Proterius, to deposition and excommunication. Whether he was banished, as well as Timothy AElurus, is not clear, but he seems to have accompanied Timothy to Alexandria, and to have been his chief supporter when, after the death of the emperor Marcian, he returned, and either murdered Proterius or excited the tumults that led to his death, A.D. 457. Timothy AElurus was immediately raised to the patriarchate by his partisans, but was shortly after banished by the emperor Leo I, the Thracian, who had succeeded Marcian. Peter also was obliged to flee. Another Timothy, surnamed Salofaciolus, a supporter of the Council of Chalcedon, was appointed to succeed Proterius in the patriarchate. When, in the following reign of Zeno, or rather during the short usurpation of Basiliscus, Timothy AElurus was recalled from exile (A.D. 475), and was sent from Constantinople to Alexandria to re- occupy that see, he was joined by Peter and his party, and with their support drove out his competitor Salofaciolus, who took refuge in a monastery at Canopus. On the downfall of Basiliscus and the restoration of Zeno, Timothy AElurus was allowed, through the emperor's compassion for his great age, to retain his see; but when on his death (A.D. 477) the Monophysite bishops of Egypt, without waiting for the emperor's directions, elected Peter (who had previously obtained the rank of archdeacon) as his successor, the emperor's indignation was so far aroused that he determined to put the new prelate to death. His anger, however, somewhat abated, and Peter was allowed to live, but was deprived of the patriarchate, to which Timothy Salofaciolus was restored. On the death of Salofaciolus, which occurred soon after, John of Tabenna, surnamed Talaia, was appointed to succeed him; but he was very shortly deposed by order of Zeno, on some account not clearly ascertained, and Peter Mongus was unexpectedly recalled from Euchaita in Pontus, whither he had been banished, and was (A.D. 482) restored to his see. His restoration appears to have been part of the policy of Zeno to unite, if possible, all parties; a policy which Peter, whose age and misfortunes appear to have abated the fierceness of his party spirit, was ready to adopt. He consequently subscribed the Henoticon of the emperor, and readmitted the Proterian party to communion on their doing the same. John of Tabenna had meanwhile fled to Rome, where the pope, Simplicius, who, with the Western Church, steadily supported the Council of Chalcedon, embraced his cause, and wrote to the emperor in his behalf. Felix II or III, who succeeded Simplicius (A.D. 483), was equally zealous on the same side. Peter had some difficulty in maintaining his position. In order to recover the favor of his Monophysite friends, whom his subservience to Zeno's policy had alienated, he anathematized the Council of Chalcedon; and then, to avert the displeasure of Acacius of Constantinople and of the court, to whose temporizing course this decisive step was adverse, he denied that he had done so. Evagrius has preserved the letter he wrote to Acacius on this occasion, which is the only writing of Peter now extant. By this tergiversation he preserved his see, and was enabled to brave the repeated anathemas of the Western Church. When, however, to recover the attachment of the Monophysites, he again anathematized the Council of Chalcedon, and Euphemius, the newly elected patriarch of Constantinople, forsaking the policy of his predecessors, took part with the Western Church against him, his difficulties became more serious. What result this combination against him might have produced cannot now be known; death removed him from the scene of strife A.D. 490, shortly before the death of Zeno. He was succeeded in the see of Alexandria by another Monophysite, Athanasius II. See Cave, Hist. Litt. 1:455; Fabricius, Bibl. Graeca, 11:336; Le Quien, Oriens Christianus, volume 2, col. 416, etc.; Tillemont, Memoires Ecclesiastiques, volume 16.