The kings of Dumnonia were the rulers of the large Brythonic kingdom of Dumnonia in the south-west of Great Britain during the Sub-Roman and early medieval periods. A list of Dumnonian kings is one of the hardest of the major Dark Age kingdoms to accurately compile, as it is confused by Arthurian legend, complicated by strong associations with the kings of Wales and Brittany, and obscured by the Saxon advance. Therefore, this list should be treated with caution.
Dumnonian kings
The original Celtic chiefs of the Dumnonii ruled in the south-west until faced with the Roman arrival into their territory in c.AD 55 when the Romans established a legionary fortress at Isca Dumnoniorum. Although subjugated by c.AD 78, the civitas Dumnoniorum was one of the regions of Roman Britain least affected by Roman influence. Known as Caer Uisc, Exeter was inhabited by Dumnonian Britons up until c.936 when King Athelstan expelled them. Several other royal residences may also have served the kings of Dumnonia or Cornwall, including Tintagel, and Cadbury Castle. ;Legendary 'Dukes of Cornwall' recorded by Geoffrey of Monmouth:
;Presumed kings appearing in the ancestry of later monarchs:
Conan Meriadoc ap Gereint
Gadeon ap Conan
Guoremor ap Gadeon
Tutwal ap Guoremor
Conomor ap Tutwal
Constantine Corneu ap Conomar
;Kings recorded in Welsh records and literature:
Erbin ap Constantine
Geraint Llyngesic ab Erbin
Cado ap Gerren
Custennin ap Cado
Gerren rac Denau ap Custennin
;William of Malmesbury:
Gwrgan: William of Malmesbury reports the terms of a grant of land made by King Gwrgan of Damnonia to the "old church" at Glastonbury in AD 601 in the time of Abbot Worgret.
Pearce identifies Constantine with the Constantine mentioned by Gildas, anchoring his reign to the 6th century, and giving later dates for the reigns of Erbin, Geraint and Cadwy.
Cornish kings
By the end of the 8th century, Dumnonia was much reduced in size by the advance of the West Saxons and the remaining territory became a rump state in Cornwall. The generally accepted date for this transition is around 800. ;Recorded in Old Welsh documents, Saints' Lives and in local and Arthurian tradition
King Mark – of Tristan and Iseult fame, probably ruled in the late 5th century. According to Cornish folklore, he held court at Tintagel.
Ricatus is mentioned on a memorial stone; he may have ruled a more localised region.
Huwal of the West Welsh, about whom there has been controversy since the 19th century. He only appears in the Anglo-Saxon Chronicle entry for 927, accepting King Athelstan of Wessex as his overlord. 'West Wales' was an old term for Dumnonia or Cornwall, but may also refer to present dayWest Wales, then generally known as Deheubarth, where Hywel Dda was king.
;The Book of Baglan An early 17th century pedigree of a so-called 'Earl of Cornwall' in the Book of Baglan may possibly represent a list of rulers in Cornwall.
In the De Gestis Herewardi Saxonis written in the 12th century it is recorded that Hereward the Wake took refuge in Cornwall in the 11th century at the court of the Cornish Prince or King Alef.
Cornish earls
If he is not to be identified with Hywel Dda of Deheubarth, the singularly recorded Huwal could have been the last native king. Some of the later supposed rulers listed below are given the title 'Earl of Cornwall', although in two cases may have been recognized as rebel kings.
Conan
Rolope ap Alanorus
Vortegyn Helin ap Rolope as 'Duke of Cornwall and Wessex'
Veffyne ap Vortegyn as 'Duke of Cornwall and Wessex'
Alured ap Veffyne as 'Duke of Cornwall and Wessex'
Cadoc's daughter Avice is said to have married William FitzRobert de Mortaigne and the title of Earl of Cornwall passed to the Normans and never returned to the native royal family.
