c. 563 (Iona) – 590 (Columbanus's continental mission); practice spread in the 7th–8th c.

Celtic missions: Patrick in Ireland, Columba at Iona, and the spread of private penance

Christianity in Ireland is traditionally linked to Patrick. He escaped Irish slavery and later, guided by a vision, returned to preach there. Untouched by invasions, Irish monasteries preserved knowledge of antiquity.

Around 563 the Irish monk Columba and twelve companions founded a monastery on the island of Iona. It became a center for mission in Scotland and later among the Angles and Saxons.

In 590 another Irish monk, Columbanus, came to Gaul. There he founded a series of monasteries, later also in Switzerland and Italy. He was eventually exiled for rebuking the morals of rulers.

In the Celtic church authority belonged to abbots rather than bishops, and it observed its own date for Easter. It developed a practice of repeatable private confession before a priest. This replaced the ancient public and unrepeatable confession. In the 7th–8th centuries wandering Celtic missionaries spread the practice throughout the Latin Church – in Gaul, Spain, and beyond.