Proterius of Alexandria was a 5th-century prelate who served as the Patriarch of Alexandria from 451 until his death in 457. He was chosen by the Council of Chalcedon to succeed Dioscorus, who had been removed from his position by the same council. His appointment caused significant religious division in Alexandria, as many local supporters of the previous leader rejected his authority. This period marked the start of a long-standing schism between the Chalcedonian and anti-Chalcedonian factions within the Alexandrian church.