|Native Name:||Teyrnas Deheubarth|
|Conventional Long Name:||Kingdom of Deheubarth|
|Boxstyle:||background: #FFFFFF; margin-left:1px; margin-right:7px; border-width:10px; border-color:#FFCC00;|
|P2:||Kingdom of Dyfed|
|S1:||Principality of Wales|
|Flag Type:||Banner of the House of Dinefwr|
|Image Map Caption:||Medieval kingdoms of Wales.|
|Year Leader1:||920 - 950|
|Leader2:||Rhys ap Tewdwr|
|Leader3:||Rhys ap Gruffydd|
|Year Leader3:||1155 - 1197|
Deheubarth was founded Circa. 920 by Hywel Dda ("Hywel the Good") out of the territories of Seisyllwg and Dyfed, both of which had come into his possession. Later on the Kingdom of Brycheiniog would also be added to its territorial boundaries. The chief seat of the rulers of Deheubarth and its traditional capital was at Dinefwr (,although Carmarthen and Cardigan also served as the Kingdoms capital at certain points).
Deheubarth, like several other Welsh kingdoms, continued to exist until the Norman Conquest of Wales, but constant power struggles meant that only for part of the time was it a separate entity with an independent ruler. It was annexed by Llywelyn ap Seisyll of Gwynedd in 1018, then by Rhydderch ab Iestyn of Morgannwg in 1023. Llywelyn ap Sisyll's son, Gruffydd ap Llywelyn again annexed Deheubarth and became ruler of most of Wales, but after his death the old Dinefwr dynasty regained power.
In church matters, Sulien of Llanbadarn (b.c. 1030) wrote many sagas and became Bishop of St. David's in 1073. Both of his sons followed him into the service of the church. (At this time the prohibition against priest marriage was not yet established.) One son, Rhygyfarch (also known as Ricemarch) of Llanbadarn Fawr wrote the Life of Saint David, and another, Ieuan of Llanbadarn Padarn was a skillful calligrapher and copyist of the works of Augustine of Hippo.
Rhys ap Tewdwr ruled from 1078 to 1093 and was able to fight off several attempts to dethrone him, considerably increasing the power of the kingdom. However the Normans were now encroaching on the eastern borders of Deheubarth, and in 1093 Rhys was killed in unknown circumstances while resisting their expansion in Brycheiniog. This led to the Norman conquest of most of his kingdom, with his son Gruffydd ap Rhys reduced to being a fugitive. Gruffydd did eventually become prince of a small part of his father's kingdom, but most was carved up into various Norman lordships.
There was a general Welsh revolt against the Normans in 1136, and Gruffydd formed an alliance with Gwynedd. Together with Owain Gwynedd and Cadwaladr ap Gruffydd of Gwynedd he won a victory against the Normans at the Battle of Crug Mawr near Cardigan. This liberated Ceredigion from Norman rule, but although it was historically part of Deheubarth it was taken over by Gwynedd as the senior partner in the alliance. Gruffydd was killed in unknown circumstances the following year.The rule of Deheubarth now fell to Gruffydd's sons, of whom four, Anarawd, Cadell, Maredudd and Rhys ap Gruffydd ruled in turn. The death of a ruler frequently led to disunity and struggles for supremacy, but the four brothers worked together to win back their grandfather's kingdom from the Normans and to expel Gwynedd from Ceredigion. Of the first three only Cadell reigned for more than a few years, but the youngest of the four, Rhys ap Gruffydd (The Lord Rhys) ruled from 1155 to 1197 and after Owain Gwynedd's death in 1170 made Deheubarth the most powerful of the Welsh kingdoms.
On Rhys ap Gruffydd's death in 1197 the kingdom was split between several of his sons, and Deheubarth did not again rival the power of Gwynedd. The early 13th century princes of Deheubarth usually appear as clients of Llywelyn the Great of Gwynedd. Following the defeat of the princes of Gwynedd and the division of their realm at the Statute of Rhuddlan, Deheubarth was divided into the historic counties of Cardiganshire, Carmarthenshire and Pembrokeshire.
Encyclopaedia of Wales [ISBN No. 978-0-7083-1953-6]