Saint Celestine I, (born , Roman Campania—died July 27, 432, Rome; feast day July 27, Irish feast day April 6), pope from 422 to 432.
He was a Roman deacon when elected on Sept. 10, 422, to succeed Boniface I. His pontificate is noted for its vigorous attack on Nestorianism, the unorthodox teaching of Patriarch Nestorius of Constantinople, which stressed that Christ’s human and divine natures were independent and which denounced the Virgin’s title Theotokos (God-bearer). Celestine also refuted the doctrine of Pelagius (fl. 405–418), which minimized the role of divine grace in man’s salvation. In 429 Celestine dispatched the French bishops SS. Germanus of Auxerre and Lupus of Troyes to combat Pelagianism in England.
After consecrating St. Palladius at Rome in 431, Celestine sent him as the first bishop to Ireland. Archbishop St. Cyril of Alexandria was entrusted with Nestorius’ recantation at the Council of Ephesus in 431. Celestine approved the council’s decision to anathematize, depose, and banish Nestorius, which caused a schism that remained unresolved for more than a century.