Flavian I of Antioch was a 4th-century prelate who served as the Patriarch of Antioch from 381 until 404. Born around 320, likely in Antioch, he chose to dedicate his significant inherited wealth and personal talents to the church. During his career, he worked alongside Diodore, the future bishop of Tarsus, to defend orthodox beliefs against the Arianism of Leontius. He was ordained as a priest by Meletius of Antioch and eventually succeeded him as patriarch.