In the wake of the breakdown of Roman rule in Britain from the middle of the fourth century, present day England was progressively settled by Germanic groups. Collectively known as the Anglo-Saxons, these included Angles, Saxons, Jutes and Frisians. The Battle of Badon was credited as a major victory for the Britons, stopping the encroachment of the Anglo-Saxon kingdoms for a period. The Battle of Deorham was critical in establishing Anglo-Saxon rule in 577. Saxon mercenaries existed in Britain since before the late Roman period, but the main influx of population probably happened after the fifth century. The precise nature of these invasions is not fully known; there are doubts about the legitimacy of historical accounts due to a lack of archaeological finds. Gildas' De Excidio et Conquestu Britanniae, composed in the 6th century, states that when the Roman army departed the Isle of Britannia in the 4th century CE, the indigenous Britons were invaded by Picts, their neighbours to the north (now Scotland) and the Scots (now Ireland). Britons invited the Saxons to the island to repel them but after they vanquished the Scots and Picts, the Saxons turned against the Britons.

An emerging view is that the scale of the Anglo-Saxon settlement varied across England, and that as such it cannot be described by any one process in particular. Mass migration and population shift seem to be most applicable in the core areas of settlement such as East Anglia and Lincolnshire, while in more peripheral areas to the northwest, much of the native population likely remained in place as the incomers took over as elites. In a study of place names in northeastern England and southern Scotland, Bethany Fox concluded that Anglian migrants settled in large numbers in river valleys, such as those of the Tyne and the Tweed, with the Britons in the less fertile hill country becoming acculturated over a longer period. Fox interprets the process by which English came to dominate this region as "a synthesis of mass-migration and elite-takeover models."