Pope Celestine I was the bishop of Rome from 10 September 422 to his death on 1 August 432. Celestine's tenure was largely spent combatting various ideologies deemed heretical. He supported the mission of the Gallic bishops that sent Germanus of Auxerre in 429, to Britain to address Pelagianism, and later commissioned Palladius as bishop to the Scots of Ireland and northern Britain. In 430, he held a synod in Rome which condemned the apparent views of Nestorius.

Palladius was the first bishop of the Christians of Ireland, preceding Saint Patrick. It is possible that some elements of their life stories were later conflated in Irish tradition. Palladius was a deacon and member of one of the prominent families in Gaul. Pope Celestine I consecrated him a bishop and sent him to Ireland "to the Scotti believing in Christ".