The Christianisation of Anglo-Saxon England was a process which began around 600 CE, influenced by Celtic Christianity from the northwest and the Roman Catholic Church from the southeast. It was essentially the result of the Gregorian mission of 597, which was joined by the efforts of the Hiberno-Scottish mission from the 630s. From the 8th century, the Anglo-Saxon mission was, in turn, instrumental in the conversion of the population of the Frankish Empire.

Augustine, the first Archbishop of Canterbury, took office in 597. In 601, he baptised the first Christian Anglo-Saxon king, Æthelberht of Kent. The decisive shift to Christianity occurred in 655 when King Penda was slain in the Battle of the Winwaed and Mercia became officially Christian for the first time. The death of Penda also allowed Cenwalh of Wessex to return from exile and return Wessex, another powerful kingdom, to Christianity. After 655, only Sussex and the Isle of Wight remained openly pagan, although Wessex and Essex would later crown pagan kings. In 686 Arwald, the last openly pagan king was slain in battle and from this point on all Anglo-Saxon kings were at least nominally Christian (although there is some confusion about the religion of Caedwalla who ruled Wessex until 688).