Prince of Deheubarth

Kingdom of Deheubarth
Teyrnas Deheubarth
920–1197
Banner of the House of Dinefwr Coat of arms
Anthem Unbennaeth Prydain "The Monarchy of Britain"
Medieval kingdoms of Wales.
Capital		Dinefwr
Languages		Welsh
Government		Monarchy
King
•	920 - 950	Hywel Dda
•	1081	Rhys ap Tewdwr
•	1155 - 1197	Rhys ap Gruffydd
Historical era		Middle Ages
•	Established	920
•	Disestablished	1197
Currency		ceiniog cyfreith & ceiniog cwta
Preceded by Succeeded by Seisyllwg Kingdom of Dyfed Principality of Wales
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Deheubarth (Welsh pronunciation: [dɛˈhəɨbarθ]; lit. "Right-hand Part", thus "the South") was a regional name for the realms of south Wales, particularly as opposed to Gwynedd (Latin: Venedotia). It is now used as a shorthand for the various realms united under the House of Dinefwr, but that Deheubarth itself was not considered a proper kingdom on the model of Gwynedd, Powys, or Dyfed is shown by its rendering in Latin as dextralis pars or as Britonnes dexterales ("the Southern Britons") and not as a named land. In the oldest British writers, Deheubarth was used for all of modern Wales to distinguish it from Y Gogledd or Hen Ogledd, the northern lands whence Cunedda and the Cymry originated.

Deheubarth was united around 920 by Hywel Dda out of the territories of Seisyllwg and Dyfed, which had come into his possession. Later on, the Kingdom of Brycheiniog was also added. Caerleon was previously the principal court of the area, but Hywel's dynasty fortified and built up a new base at Dinefwr, near Llandeilo, giving them their name.

After the high-water mark set by Hywel, Dinefwr was repeatedly overrun. First, by the Welsh of the north and east: by Llywelyn ap Seisyll of Gwynedd in 1018; by Rhydderch ab Iestyn of Morgannwg in 1023; by Gruffydd ap Llywelyn of Gwynedd in 1041 and 1043. In 1075, Rhys ab Owain and the noblemen of Ystrad Tywi succeeded in treacherously killing their English-backed overlord Bleddyn ap Cynfyn. Although Rhys was quickly overrun by Gwynedd and Gwent, his cousin Rhys ap Tewdwr – through his marriage into Bleddyn's family and through battle – reëstablished his dynasty's hegemony over south Wales just in time for the second wave of conquest: a prolonged Norman invasion under the Marcher Lords. In 1093, Rhys was killed in unknown circumstances while resisting their expansion into Brycheiniog and his son Gruffydd was briefly thrown into exile.