Basil of Seleucia was a 5th-century Roman archbishop and ecclesiastical writer who served the see of Seleucia ad Calycadnum. A significant figure during the Eutychian controversy, he participated in several major councils, including the Synods of Constantinople and Ephesus. While his political stances shifted during the theological turmoil of the era, he maintained a consistent Christological belief in the dual nature of Christ. He is particularly noted for contributing to the theological language used in the Chalcedonian definition regarding the two natures of Jesus.