Research Notes:

The Dumnonii or Dumnones were a Celtic tribe who inhabited part of the South West peninsula of Britain, during the Iron Age and the early Roman period.

The Dumnonii are thought to have occupied territory in Somerset, Devon and Cornwall and possibly part of Dorset. They do not seem to have been politically centralised: the structure, distribution and construction of Bronze Age and Iron Age hillforts in the south west point to a number of smaller tribal groups living alongside each other.

Ptolemy's 2nd century Geography, places the Dumnonii to the west of the Durotriges, and names four of their towns: Isca Dumnoniorum (later Caeresk, now Exeter), Tamara (presumably on the River Tamar), Uxella (perhaps on the River Axe) and Voliba (unidentified). The Ravenna Cosmography adds the names of two more settlements: Nemetostatio, a name relating to nemeto-, sanctuary or sacred grove (Probably to be identified with North Tawton, Devon) and Durocornavium (unidentified, but possibly Tintagel or Carn Brea). The name Durocornavium implies the existence of a tribe called the Cornavii, perhaps the ancestors of the Cornish people (although some trace the Cornish to an unlikely hypothetical migration of the Cornovii of the West Midlands). See the article Cornovii (Cornish) for further information.

In the sub-Roman period a Brythonic kingdom called Dumnonia emerged, covering the entire peninsula, although it is believed by some to have effectively been a collection of sub-kingdoms.

The Dumnonii would have spoken a Brythonic dialect ancestral to modern Cornish.

Victorian historians often referred to this tribe as the Damnonii, which is also the name of another Celtic people from lowland Scotland, although there are no known links between the two populations. Another tribe with a similar name (but with no known links between the two) appear to have had a presence also in Ireland, as shown by the presence of a people called the Fir Domnann in the province of Connacht.

The god worshiped by the Dumnonii was known as 'Dumnonos'