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Celtic Kingdoms of the British Isles

Celts of Cymru


Map Deheubarth

The kingdom of Deheubarth (pronounced de-hay-bath), was formed as a unified state comprising much of Dyfed's territory, along with all of Ystrad Towi and Ceredigion. Cymru had been unified under Rhodri Mawr, and his descendants eventually ruled large areas of the country, often with traditional borders changed by the shake-up.

Under the rule of the kings of Deheubarth, the territory included modern Dyfed (old Carmarthanshire, Pembrokeshire and Cardiganshire, or Ceredigion), and Brycheiniog (now in southern Powys). It also occasionally included Gwynedd, but usually only when Gwynedd's king was also king of Deheubarth (deheu means 'of the south', the kingdom's obvious power base).

(Additional information by Hywel George.)

844 - 873

Rhodri Mawr (the Great)

King of Wales (Gwynedd, Dyfed & Seisyllwg).


The Chronicle of the Princes reports that 'Saxons' (probably from Mercia) invade Anglesey. Meurig ap Hywel of Gwent is said to join Rhodri the Great, king of Wales (Gwynedd and Deheubarth), in defeating them but falls during the battle. The Annales Cambriae also record the death of Meurig at the hands of Saxons.

872 - 873

The death of Gwgan ap Meurig of Seisyllwg means that his kingdom passes to his brother-in-law, Rhodri Mawr. Rhodri is now king of all Wales, and in 873 he institutes a form of devolved government in which three of his sons control parts of the country in his name. Anarawd is granted Deheubarth, Cadell governs Seisyllwg, and Merfyn commands in Powys.

873 - 916

Anarawd ap Rhodri

King of Deheubarth (and Gwynedd in 878).


Upon the death of Rhodri Mawr, and according to his wishes, Wales is officially divided between his sons. Anarawd succeeds him in Deheubarth and gains Gwynedd, Merfyn is confirmed in Powys, and Cadell in Seisyllwg.


MapHywel Dda is the son of Cadell of Seisyllwg and king of Dyfed (and therefore the nephew of Anarawd). He rules the latter from 904 and in 916 becomes king of Deheubarth, creating a permanent greater South Wales kingdom. When he becomes king of Gwynedd in 942 he is able to create a United Wales. Once Gwynedd becomes detached from the remainder of the territory, former Dyfed provides the heartland along with Ceredigion of the kingdom of Deheubarth.

916 - 950

Hywel Dda (the Good) ap Cadell

King of Wales (Dyfed (904-916), Gwynedd (942-950) & Seisyllwg).


MapHywel effectively forces the king of Brycheiniog to become sub-king to Deheubarth.


Æthelstan of Wessex and all the English meets with several northern kings at the convention of Eamont (near Penrith) and later meets with the Welsh monarchs, including those of Deheubarth, Glywyssing, and Gwent. All accept him as their overlord. Once he assumes overlordship of British Corniu, and ousts the Danish king of York, all in the same year, he is well and truly king of England.


Hywel Dda gains Gwynedd upon the death of Idwal Foel and grabs Powys, making him sole ruler of all Wales. He has already acknowledged the late Athelstan of Wessex as his overlord and has associated himself closely with the English king, witnessing Athelstan's grants of lands and charters (the British Museum possesses a charter which records a grant of land by Athelstan at Luton in 931, and which bears the testimony: 'Ego Howael subregulus consensi et subscripsi' (Sub-King Hywel hereby consents and agrees')).

It is clear that Wales is now sharply divided between a strong anti-English party, based chiefly in the north and led by the sons of Rhodri Mawr in Gwynedd, and a South Welsh party which favours union with England. Hywel is the leader of the latter, and his epithet 'dda' is given to no other Welsh king. It is probably first given to him by the South Wales 'unionists'; the epithet 'mawr' that had been applied to Rhodri Mawr had probably arisen as an expression of the traditionally more exclusive nationalist policy of the North Welsh. These conflicting views dominate Welsh politics for the next couple of centuries.


Cadwgan, son of Owain and grandson of Hywel Dda, is killed by the Saxons of England. In the same year a battle takes place at Carno between the sons of Idwal Foel of Gwynedd and the sons of Owain ap Hywel Dda. The men of Gwynedd manage to devastate areas of Dyfed, presaging a great deal of future conflict between the two greatest states of Wales.


The death of Hywel Dda, king of all Wales, leaves the country divided. Hywel's sons, Owain, Rhun, Rhodri and Edwyn, take possession of his estates in South Wales, with Rhodi becoming king of Deheubarth itself and Owain becoming prince of Ceredigion (Seisyllwg). Iago and Ieuaf, the sons of Idwal Foel, seize North Wales as their birthright (Gwynedd and Powys). The two sides disagree strongly over the break-up of a united Wales, but the joint kings of Gwynedd cannot be removed, despite a raid into Dyfed which sees many of their men cut down by Owain's force from Ceredigion. Morgannwg continues to retain its independence under its own line of kings.

950 - 957

Rhodri ap Hywel Dda

Ruled all but Gwynedd, under Iago.


Rhodri's brother, Owain, succeeds to the throne of Deheubarth and Ceredigion (Seisyllwg) is fully reunited with it under him as its single ruler.

957 - 986

Owain ap Hywel Dda

Ruled all but Gwynedd, under Iago & Hywel the Bald.

986 - 1023

Under the dominion of Gwynedd. King Llywelyn ap Seisyll of Gwynedd dies unexpectedly and Rhydderch ap lestyn seizes the throne of Deheubarth by force, albeit holding onto it briefly.


Rhydderch ap lestyn

King of Morgannwg. Usurper.

1023 - 1033

Iago ap Idwal swiftly pushes out Rhydderch and re-establishes the domination of Gwynedd over south-west Wales.


Hywel ab Edwin

1033 - 1035

Maredudd ab Edwin


1039 - 1042

Under the dominion of Gwynedd.

1042 - 1044

Hywel ab Edwin

Second time.


Upon the death of the last king of Brycheiniog, the kingdom is divided between his sons, and all effective power passes to Deheubarth. More concretely fixed to 1045 is the fact that Gruffydd ap Rhydderch of Morgannwg is able to seize Deheubarth from Gruffydd ap Llywelyn of Gwynedd and hold onto it for a decade until the tables are turned.

1055 - 1063

Gruffydd ap Llywelyn of Gwynedd invades and conquers Morgannwg and Gwent, subjugating them both and drawing them directly under his control along with Deheubarth as part of a united Wales. Following his death, united Wales breaks up, and Deheubarth's native rulers are apparently able to seize control.


Maredudd ab Owain ab Edwin

Rule uncertain.

1063 - 1072

Under the dominion of Gwynedd.

1066 - 1068

The last native British earl of Corniu (Cornwall) is deposed by William in 1066 as he tightens his grip on the newly-conquered kingdom of England. At first, only the south-east can be considered as being securely held. Princes Blethyn and Rhiwallon ap Cynfyn of Gwynedd, Deheubarth, and Powys resist the invaders as part of their supporting role for Harold Godwinson. They join Eadric the Wild of Mercia in an attack on Norman forces at Hereford in 1067, and Earl Edwin of Mercia with Earl Morcar of Northumbria in a further attack in 1068.

The Norman conquest of Britain owed much to good fortune, but once achieved it was enforced by military strength and a prolific castle-building programme


Rhys ab Owain

1072 - 1078

Under the dominion of Gwynedd.

1078 - 1093

Rhys ap Tewdwr Mawr

Ruled all but Gwynedd, under Gruffydd ap Cynan.


Attempting to emulate the achievements of his father and grandfather and become king of South Wales, Caradoc ap Gruffydd of Morgannwg drives Rhys ap Tewdwr Mawr from his throne. He is immediately faced by the threat of that king returning in alliance with Gruffydd ap Cynan, who is pursuing his own claim for the throne of Gwynedd. Gruffydd also gains the cooperation of his nemesis in Gwynedd, Trahaern ap Caradog, and Meilir ap Rhiwallon of Powys. Caradoc is killed at the Battle of Mynydd Carn, as are Trahaern and Meilir, allowing Gruffydd to seize his birthright in Gwynedd and Rhys to regain Deheubarth.

1093 - 1113

Rhys ap Tewdwr Mawr has been successful in fighting off several attempts to dethrone him, but now he dies in mysterious circumstances while resisting the expansion of Norman power in neighbouring Brycheiniog. It may be Bernard de Neufmarché, the Norman lord who has taken control of Brycheiniog, who slays him. His son, Gruffydd ap Rhys, is forced to flee, becoming a fugitive for a time before he can escape to Ireland. Deheubarth has apparently been conquered, and is carved up between rival Norman lords, each taking their share of the existing cantrefi or lordships.

1113 - 1114

Gruffydd ap Rhys returns from Ireland intent on reclaiming the throne of South Wales which is in the hands of the Norman king. Henry II sends orders to have him arrested but he finds refuge with Gruffydd ap Cynan in Gwynedd. Received at the palace of Aberffraw with full honours, he is soon joined by his brother, Hywel ap Rhys, who has escaped from years of imprisonment at Montgomery Castle under the watchful eye of Arnulp de Montgomery.

Henry destroys the impending Welsh alliance by offering Gruffydd ap Cynan gifts of tribute-free lands, and the brothers are forced to flee to Ceredigion and the wilds of Ystrad Towy. From there they begin to attack Norman strongholds in Ceredigion and North Pembroke (the heartland of former Dyfed). Several castles are destroyed or severely damaged while England suffers from a plague and is unable to respond. Flemish mercenaries are offered lands in Wales, particularly in Pembroke, in return for stemming the advance, and Gruffydd is only able to restore a reduced Deheubarth, with the rest still being held by Norman lords.

1113 - 1135

Gruffydd ap Rhys

Son. Ruled a reduced Deheubarth.

1135 - 1137

Under the dominion of Gwynedd?

1137 - 1143

Anarawd ap Gruffydd

Ruled all but Gwynedd, under Owain Gwynedd.

1143 - c.1151

Cadell ap Gruffydd

c.1151 - 1155

Maredudd ap Grufydd

1155 - 1197

Rhys ap Gruffydd

'The Lord Rhys'.


Following the death of the Lord Rhys, what is left of his kingdom in the face of increasing pressure by the Normans is divided between his warring sons.

1196 - 1202

Gruffydd ap Rhys

Ruled from May 1196.

1202 - 1236

Owain ap Gruffydd

Last independent Welsh prince of South Wales.


The power of Deheubarth has been declining for years, and by this point the practical end of the dynasty has arrived. Deheubarth is subjugated under Plantagenet rule.

One of the kingdom's royal sons, Owain Glyndwr, Prince of Wales, later leads a rebellion against Wales' overlords which ends in 1416. In 1284 the Statute of Rhuddlan divides the Dyfed region of Deheubarth into the counties of Carmarthenshire (which contains only a small, eastern part) and Pembrokeshire (which contains much of Dyfed). Both counties survive in use today.