Sub-Roman Britain is a term derived from an archaeological label for the material culture of Great Britain in Late Antiquity, the transition period between the Roman Empire's Crisis of the Third Century around 235 A.D. (and the subsequent collapse and end of Roman Britain), until the start of the Early Medieval period. The term "Post-Roman Britain" is also used for the period, mainly in non-archaeological contexts.

Sub-Roman Britain is a term derived from an archaeological label for the material culture of Great Britain in Late Antiquity, the transition period between the Roman Empire's Crisis of the Third Century around 235 A.D. (and the subsequent collapse and end of Roman Britain), until the start of the Early Medieval period. The term "Post-Roman Britain" is also used for the period, mainly in non-archaeological contexts.