Nestorius (c. 386 – c. 451) was Patriarch of Constantinople from April 10, 428 to June 22, 431. He received his clerical training as a pupil of Theodore of Mopsuestia in Antioch and gained a reputation for his sermons that led to his enthronement by Theodosius II as Patriarch following the death of Sisinius I in 428 AD.
Nestorius is considered to be the originator of the Christological heresy known as Nestorianism, which emerged when he began preaching against the new title Theotokos or Mother of God, beginning to be used of the Virgin Mary. His immediate antagonist was Cyril, bishop of Alexandria. Although Nestorius did deny the Virgin Birth of Jesus, he did not in fact maintain the heresy which bears his name.