The Cornovii is a hypothetical name for a tribe presumed to have been part of the Dumnonii, a Celtic tribe inhabiting the south-west peninsula of Great Britain, during some part of the Iron Age, Roman and post-Roman periods. The Cornovii are supposed to have lived at the western end of the peninsula, in the area now known as Cornwall, and if the tribal name were correct it would be the ultimate source of the name of that present-day county.