In this chapter, the author provides a historic overview of Christian Ireland in the early middle ages. He then evokes some salient features of early Irish Christianity, both in its material and in its spiritual aspects. The author examines both the universal Catholic mould and the distinctively Gaelic stamp of early Irish Christianity. He concludes by looking at some of the ways in which it has dealt with the pre-Christian past and contributed to shaping the future. The interaction of Gaelic and Catholic in the early middle ages has to be seen in the context of a dynamic history following the Celticisation of Ireland and the Romanisation of western Britain. Historically, Irish penitentials were to be of special significance, as they were of crucial importance for the development of the practice of penance in the middle ages.