Christianity was introduced in the 5th century. This is traditionally associated with St Patrick (d. 461) although there were some Christians in the country before his arrival. The first written documents date from this period. A distinctive feature of the development of early Irish Christianity was the important role played by monasticism. The great monasteries such as Glendalough, founded by St Kevin, and Clonmacnoise, founded by St Ciaran, were famous centres of culture and learning and the illuminated manuscripts which they produced were among the glories of Irish monasticism.
It was through the monasteries that Irish influence on Britain and Europe was exerted from the 6th century onwards. Setting out first as pilgrims, Irish monks preached the Gospel and established new communities across the continent. Ireland, unlike most of the rest of Europe, did not suffer barbarian invasion and so acted as a repository of Christian civilization at a time when it was almost extinguished elsewhere. Irish monks are associated with a number of continental centres - St Fursey at Peronne in France, St Kilian at Wurzburg in Germany, St Vergil at Salzburg in Austria, St Columbanus at Bobbio in Italy. They brought Christianity to pagan peoples, established centres of learning and paved the way for the intellectual flowering in 9th century France known as the Carolingian Renaissance. One of the most notable of these monks was the philosopher and
theologian Johannes Scotus Eriugena.
The successful missionary efforts of the Irish abroad were matched by rich cultural achievements at home. Elaborate chalices, croziers and ornamental jewellery were fashioned while the scribes committed the rich classical tradition to their magnificently illuminated manuscripts. This period from the 6th to the 9th century has been seen by many as the Golden Age of Irish history.