Anglo-Saxon missionaries were instrumental in the spread of Christianity in the Frankish Empire during the 8th century, continuing the work of Hiberno-Scottish missionaries which had been spreading Celtic Christianity across the Frankish Empire as well as in Scotland and Anglo-Saxon England itself during the 6th century. Both Ecgberht of Ripon and Ecgbert of York were instrumental in the Anglo-Saxon mission. The first organized the early missionary efforts of Wihtberht, Willibrord, and others; while many of the later missioners made their early studies at York.

The Hiberno-Scottish mission was a series of expeditions in the 6th and 7th centuries by Gaelic missionaries originating from Ireland that spread Celtic Christianity in Scotland, Wales, England and Merovingian France. Celtic Christianity spread first within Ireland. Since the 8th and 9th centuries, these early missions were called 'Celtic Christianity'.