Christianity was present in Roman Britain from at least the third century until the end of the Roman imperial administration in the early fifth century, and continued in western Britain.

In the seventh century the pagan Anglo-Saxons were converted to Christianity mainly by missionaries sent from Rome. Irish missionaries from Iona, who were proponents of Celtic Christianity, were influential in the conversion of Northumbria, but after the Synod of Whitby in 664, the Anglo-Saxon church gave its allegiance to the Pope.