Saint Eustathius, Archbishop of Antioch (323-331) was born in Side Pamphylia in the second half of the third century. He was bishop of the city of Beria, enjoyed the love and respect of the people, and at the request of his flock was elevated by the fathers of the First Ecumenical Council (325) to the See of Antioch. Saint Eustathius was a deeply educated theologian, and was also distinguished by his extensive knowledge of secular sciences. When the heresy of Arius began to spread in the East, which did not recognize the Consubstantiality of the Son of God with the Father, Saint Eustace zealously fought – verbally and in writing – for the purity of the Orthodox faith. 
In 325, the First Ecumenical Council of Nicaea was convened by the Holy Equal-to-the-Apostles Tsar Constantine the Great (306-337). The first chairman of this Council was St. Eustathius. The Council condemned Arius' teaching and set out the Orthodox confession in the Symbol of Faith. The Council defrocked and excommunicated the violent Arius, as St. Eustathius called him, who did not want to give up his error, and his associates. However, among the bishops who signed the Nicene Symbol, there were also those who sympathized with the heresy of Arius and signed the acts of the Council not out of conviction, but out of fear of excommunication. After the Council, their intrigues against St. Eustace began. With great cunning, they obtained his consent to convene a Local Council in Antioch. Having bribed one harlot, they persuaded her to come to the Council with a baby and perjure herself that St. Eustathius was the father of the baby. Violating the apostolic rules that an accusation against a clergyman should be accepted with the confirmation of two witnesses, the Arians declared St. Eustathius deposed. He was exiled to Thrace without trial. But the falsity of the accusation was soon revealed: seriously ill after the slander, the woman repented, called the clergy and confessed her sin in the presence of many people. However, by this time Saint Constantine the Great had died, and his son Constantius (337-361), who shared the heretical views of Arius and patronized the Arianist bishops, ascended the throne. Saint Eustathius still zealously fought for Orthodoxy in exile. He died in exile in Philippi or Traianopolis in 337.
The Second Ecumenical Council, held in Constantinople in 381, confirmed the Orthodox Creed, which St. Eustathius so zealously defended. The Arian false doctrine was once again anathematized as heresy.
In 482, the relics of St. Eustace were honorably transferred from Philippi to Antioch, to the great joy of the Antiochians, who never ceased to honor and love their patriarch-confessor.
Saint Eustace was revered by the great fourth-century saints Basil the Great, John Chrysostom, Athanasius of Alexandria, Epiphanius of Cyprus, Anastasius of Sinai, and Jerome of Stridon. The well-known church historian Bishop Theodoret of Kyra calls Saint Eustace a pillar of the Church and piety, along with Saint Athanasius of Alexandria and other bishops, the main champions of Orthodoxy.