Diodorus of Tarsus was a 4th-century Christian bishop, theologian, and monastic reformer born in Antioch. A dedicated defender of Nicene orthodoxy, he resisted the paganism promoted by Emperor Julian and actively opposed Arianism and Apollinarianism. He established a significant monastic and catechetical center near Antioch, which became the foundation for the Antiochene School of thought. Throughout his career, which included serving as the bishop of Tarsus, he participated in major ecclesiastical gatherings such as the Council of Constantinople and remained a prominent figure in the theological developments of his era.