Sub-Roman Britain is a term derived from an archaeological label for the material culture of Britain in Late Antiquity: the term "Sub-Roman" was invented to describe the potsherds in sites of the 5th century and the 6th century, initially with an implication of decay of locally-made wares from a higher standard under the Roman Empire.

It is now often used to denote a period of history.

Although the culture of Britain in the period is mainly derived from Roman and Celtic sources, there are also Saxons settled as foederati in the area, originally from Saxony in northwestern Germany, although the term 'Saxon' is used by the British for all Germanic incomers.

Gradually the latter assume more control.

The Picts in northern Scotland are also outside the applicable area.