Rhodri the Great

Rhodri ap Merfyn (c. 820–878), later known as Rhodri the Great (Welsh: Rhodri Mawr), succeeded his father, Merfyn Frych, as King of Gwynedd in 844. Rhodri annexed Powys c. 856 and Seisyllwg c. 871. He is called "King of the Britons" by the Annals of Ulster. In some later histories, he is referred to as "King of Wales", although the title is anachronistic and his realm did not include southern Wales.

Rhodri was the son of Merfyn Frych, who had claimed Gwynedd upon the extinction of Cunedda's male line. Rhodri then inherited the realm after his father's death around 844. Merfyn hailed from "Manaw" which may either refer to the Isle of Man or Manau, the ancestral homeland of all Gwynedd's kings since Cunedda.

According to later genealogies, his mother or grandmother was Nest ferch Cadell of the ruling dynasty in Powys. Although surviving texts of Welsh law expressly forbid inheritance along the maternal line, Nest and Rhodri's supposed inheritance was later used to justify Gwynedd's annexation of Powys after the c. 855 death of Cyngen ap Cadell in preference to Cyngen's other heirs.

Similarly, Rhodri's marriage to Angharad ferch Meurig was used to explain his supposed inheritance of her brother Gwgon's kingdom of Ceredigion after that king's death in 872 via a principle of jure uxoris that does not survive in our sources for Welsh law.

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