Dictionary of National Biography, 1885-1900/Rhodri Mawr
RHODRI Mawr, i.e. The Great (d. 877), Welsh king, was the son of Merfyn Frych [q. v.], on whose death in 844 he became ruler of North Wales. According to Jesus Coll. MS. 20 (Cymrodor, viii. 87), he was the son of Nest, heiress of Powys, and grandson of ‘Ethellt,’ heiress of Gwynedd; later authorities (‘Gwentian Brut,’ Powel, Carnhuanawc) reverse the two names. By his marriage with Angharad, daughter of Meurig ap Dyfnwallon, he became, on the death (in 871) of Gwgon, her brother, ruler of Ceredigion and Ystrad Tywi also; his realm then extended from Anglesey to Gower, though hemmed in on the west by Dyfed (extending from St. David's to Carmarthen), and on the east by principalities occupying the modern Radnorshire, Brecknockshire, and Glamorganshire. It was probably against Rhodri, who was an active and energetic prince, that Burhred of Mercia in 853 sought the help of his overlord Ethelwulf; the West-Saxon king led an expedition into Wales, which for a time re-established the Mercian supremacy. But Rhodri was chiefly occupied in withstanding the incursions of the Danes, who, with the ‘Dubh Gaill,’ or ‘gentiles nigri’ of the Menevian annals, appeared in the Irish Sea from about 850, and began to press hardly on Wales. Irish chronicles tell how he slew a Danish leader ‘Horm’ in 855; in 876 he suffered a reverse, probably the ‘battle in Anglesey on a Sunday’ recorded under that year in ‘Annales Cambriæ,’ which compelled him to flee to Ireland. In the following year both he and his son (or brother?) Gwriad were slain by the English, a blow so keenly felt by his subjects that a victory over the English won on the banks of the Conway three years later came to be known as ‘God's vengeance for Rhodri.’
According to Asser, Rhodri left six sons, of whom he mentions Anarawd as the leader (Mon. Hist. Brit. p. 488). Two others, Cadell and Merfyn, are named by early authorities; as to the other three there is some discrepancy. A tradition, of the existence of which in the time of Giraldus Cambrensis there is evidence, asserts that on their father's death, Anarawd, Cadell, and Merfyn divided his dominions among them, taking Gwynedd, South Wales, and Powys respectively (Gir. Cambr. Descriptio Kambriæ, i. 2). It is certain that Anarawd and Cadell founded the royal houses of Gwynedd and Deheubarth; Merfyn appears to have transmitted no princely claims, and his possession of Powys is unattested. In later times the story ran that Rhodri himself made the partition, assigning a royal court to each of the three sons, and arranging for the supremacy of the eldest over the other two (Gwentian Brut in Myv. Arch. 2nd ed. p. 688, Sir John Price in the ‘description’ prefixed to Powel's Historie, Humphrey Llwyd and Powel in the Historie itself). A document in the Iolo MSS. (pp. 30–1) adds the provision made by Rhodri for the settlement of disputes between two of the three princes. In the sixteenth and seventeenth centuries there was much debate among the antiquaries of Wales as to whether Anarawd or Cadell were the eldest and therefore the privileged son, North and South Wales being at issue upon the matter. A full discussion of the topic from the northern point of view may be found in Vaughan of Hengwrt's ‘British Antiquities Revived’ (1662, reprinted at Bala in 1834).
[Chronicle and Genealogies in Harl. MS. 3859, as printed in Cymrodor, vol. ix.; Jesus Coll. MS. 20, as printed in Cymrodor, vol. viii.; Anglo-Saxon Chronicle; Annals of Ulster; Chronicon Scotorum, Rolls ed.]