Dyfed
Deheubarth was a medieval kingdom in Wales that emerged as a distinct political entity in the post-Roman period.
Deheubarth | History
Early Medieval Period | 7th – 9th centuries
The name Deheubarth translates to “the southern part” in Welsh, signifying its location in the southern region of Wales. It emerged as an independent kingdom during the early Middle Ages, and its rulers played significant roles in Welsh politics and history. The kingdom was formed through the unification of several smaller Welsh kingdoms, including Seisyllwg, Dyfed, and parts of Brycheiniog.
Hywel Dda | 9th – 10th centuries
Hywel Dda, or Hywel the Good, ruled Seisyllwg and became a key figure in the history of Deheubarth during the late ninth and early tenth centuries. Hywel Dda is credited with unifying various Welsh kingdoms, including Dyfed, under the banner of Deheubarth. His reign is notable for the codification of Welsh laws known as Cyfraith Hywel or the Laws of Hywel.
Under the rule of Hywel Dda and his successors, Deheubarth expanded its influence and control over other Welsh territories. At its height, the kingdom encompassed a significant portion of southern Wales, extending from Pembrokeshire to the Gower Peninsula and parts of Ceredigion and Carmarthenshire. Like other Welsh kingdoms, Deheubarth faced internal conflicts and external threats from neighboring kingdoms and Anglo-Norman forces. The kingdom went through periods of fragmentation and reunification under different rulers.
Norman Invasions | 11th – 12th centuries
Deheubarth faced challenges from Norman invaders during the eleventh and twelfth centuries. Norman lords, including figures like Bernard de Neufmarché and Roger of Montgomery, sought to expand their territories into Welsh lands. This led to conflicts and territorial changes, and Deheubarth’s last king, Rhys ap Gruffydd (known as Lord Rhys), struggled to maintain autonomy against Norman advances.
By the late twelfth century, Deheubarth was effectively integrated into the emerging Principality of Wales, under the rule of the English crown. This marked the end of its existence as an independent kingdom.
Source
Kings and Princes of Deheubarth | David Nash Ford’s Early British Kingdoms