Theodoret of Cyrus or Cyrrhus (; c. AD 393 – c. 458/466) was an influential theologian of the School of Antioch, biblical commentator, and Christian bishop of Cyrrhus (423–457). He played a pivotal role in several 5th-century, Byzantine Church controversies that led to various ecumenical acts and schisms. He is called "blessed" in the Eastern Orthodox Church, and some Chalcedonian and East Syrian Christians regard him as a saint.