Britannia Inferior (Lower Britain) was one of the regions of Roman Britain created in the early third century AD by the Roman Emperor Septimus Severus.

The governors of Lower Britain were of Praetorian rank although few are known by name. They were therefore outranked by the consular governors of Britannia Superior. Their capital was at Eboracum (York).

Epigraphic evidence has shed some light on the extent of Lower Britain and it encompassed all of what is now northern England from the Pennines to Hadrian's Wall. During the early fourth century, the province was divided into Britannia Secunda in the north (with a capital at York) and Flavia Caesariensis in the south (with a capital at Lincoln). Later still, another province, named Valentia was likely created from its northernmost extent.