Hywel Dda unites the kingdoms of Dyfed and Seisyllwg to create Deheubarth.
The local health board of south-west Wales also bears his name.
Hywel Dda | Hywel Bennett | Saint Hywel | Owain ap Hywel Dda | Hywel Williams | Hywel Dda Local Health Board | Hywel ap Rhys | Hywel ap Rhodri Molwynog | Hywel ab Owain Gwynedd |
Hyfaidd's sons Llywarch and Rhodri reigned after him, but the kingdom was soon lost to Cadell's son Hywel who consolidated his realms as Deheubarth.
His legacy endured in the form of his laws, which remained in active use throughout Wales until the appointed date of implementation of the Laws in Wales Acts 1535–1542 of Henry VIII of England who asserted his royal descent by blood-line from the House of Aberffraw, via Rhodri Mawr via Hywel Dda.
Geoffrey's Cligueillus / Digueillus may be a corruption of the Old Welsh name Higuel (specifically, the 10th century AD king Higuel (Howel/Houuel) Bonus - i.e. Hywel Dda - mentioned in one of Geoffrey's sources, the Annales Cambriae, now Modern Welsh Howell.