Hywel Dda (c.880–950), (English Hywel the Good, sometimes anglicized to Howell the Good) was originally king of Deheubarth in south-west Wales but eventually came to rule most of Wales. As a decendent of Rhodri Mawr through his father Cadell, Hywel was a member of the Dinefwr branch of the dynasty.
He is remembered as one of the most successful native Welsh rulers prior to the Norman Conquest. His name is particularly linked with the development of the Welsh laws, often called the Laws of Hywel'.
Hywel was born in around 880, the younger son of Cadell ap Rhodri, himself the son of Rhodri the Great. In 905, Cadell, having conquered Dyfed, gave it to his son to rule on his behalf. Hywel was able to consolidate his position by marrying Elen, whose father had ruled Dyfed until his death. Following his father's death in 909, he acquired a share of Seisyllwg, and on his brother's death in 920, he merged Dyfed and Seisyllwg, creating for himself a new kingdom, which became known as Deheubarth. Following the death of his cousin Idwal Foel in 942, he also seized the principality of Gwynedd, becoming ruler of about three-quarters of present-day Wales.
Hywel's reign, uncharacteristically for the time, was a peaceful one, and he achieved an understanding with Athelstan of England. Such was the relationship between the neighbouring countries that Hywel was able to mint his own coinage in the English city of Chester. He was the only Welsh ruler ever to produce coinage. His study of the English legal system and his visit to Rome in 928 (on a pilgrimage) combined to enable him to formulate advanced ideas about government. (He would possibly have a chance to meet either of the Popes John X, Leo VI and Stephen VIII who were active during that year).
Opinions vary as to the motives for Hywel's close association with the court of Athelstan. J.E. Lloyd saw him as an enthusiastic anglophile and admirer of the kings of Wessex, while D.P. Kirby suggests that it may rather be the action of a pragmatist who recognized the realities of power in mid-10th century Britain. It is notable that he gave one of his sons an Anglo-Saxon name, Edwin. His policies with regard to England were evidently not to the taste of all his subjects. A Welsh language poem entitled Armes Prydein, considered by Sir Ifor Williams to have been written in Deheubarth during Howell's reign, called for the Welsh to join a confederation of all the non-English peoples of Britain and Ireland to fight the Saxons. The poem may well be linked to the alliance of Norse and Celtic kingdoms which challenged Athelstan at the Battle of Brunanburh in 937. No Welsh forces joined this alliance, and this may well be because of the influemce of Hywel; on the other hand neither did he send troops to support Athelstan.
The conference held at Whitland in about 945, was a kind of parliament in which Welsh law was codified and set down in writing for posterity, much of the work being done by the celebrated clerk, Blegywryd. Following Hywel's death, his kingdom was soon split into three. Gwynedd was reclaimed by the sons of Idwal Foel, while Deheubarth was divided between Hywel's sons. However, his legacy endured in the form of his enlightened laws, which remained in active use throughout Wales until the conquest and were not abolished by the English Parliament until the 16th century.