Cynan Dindaethwy (English: "Cynan of Dindaethwy") or Cynan ap Rhodri ("Cynan son of Rhodri") was a king of Gwynedd (reigned c. 798 – c. 816) in Wales of the Early Middle Ages. Cynan was the son of Rhodri Molwynog and ascended to the throne of Gwynedd upon the death of King Caradog ap Meirion in 798. His epithet refers to the commote of Dindaethwy in the cantref Rhosyr. Unlike later kings of Gwynedd, usually resident at Aberffraw in western Anglesey, Cynan maintained his court at Llanfaes on the southeastern coast. Cynan's reign was marked by a destructive dynastic power struggle with a rival named Hywel, usually supposed to be his brother.
There is no historical record of Cynan's early years as king, but his reign ended in a combination of natural disasters and military reverses. In 810, there was a bovine plague that killed many cattle throughout Wales. The next year Deganwy, the ancient wooden court of Maelgwn Gwynedd, was struck by lightning.
A destructive war between Cynan and Hywel raged on Anglesey between 812 and 816, ultimately ending with Cynan's defeat and banishment. Cynan and Hywel are said to be brothers in historical works such as Lloyd's History of Wales, although Lloyd does not cite its source. The Annals of Wales mention the pair only by name, without any title, relation, or patronym. (In comparison, it takes care to point out the brotherly nature of Elisedd's slaughter of Gruffydd ap Cyngen in Powys around the same time.) The genealogies from Jesus College MS 20 deny Cynan and Hywel were brothers at all, instead making Hywel the son of Caradog ap Meirion and a distant cousin of Cynan Dindaethwy son of Rhodri Molwynog. The Harleian genealogies agree with this. Cynan died within a year of his exile according to the Annals of Wales and the Irish Annals.
- Lloyd 1911:232, A History of Wales, Vol I
- Lloyd 1911:231, A History of Wales
- Phillimore 1888:163–164, Annales Cambriae
- Phillimore 1887:89 — his pedigree is given as: Howel. M. Crada6c. M. meircha6n. M. Howel. M. Runya6n. M. Einya6n. M. Idwm. M. Cadwall. M. meic. M. Ewein. M. Cenlas. M. Ewein danwyn. M. Einya6n yrth. M. Cuneda Wledic.
- Phillimore 1887:87 — his pedigree is given as: ... Cynan tintaeth6y. M. Rodri mol6yna6c. M. Idwal I6rch. M. Kadwaladyr vendigeit. M. Katwalla6n. M. Kad6ga6n. M. Iago. M. Beli. M. Run hir. M. Maelg6n g6yned ..., and from there back to Cunedda.
- Owen 1841:xiv, Pedigree of Ywain Son of Hywel, in the Preface of Ancient Laws and Institutes of Wales — his pedigree is given as: ... Rotri Map Mermin Map Ethil Merch Cinnan Map Rotri M. Tutgual M. Catgualart M. Catman M. Jacob ..., and from there back through Maelgwn Gwynedd to Cunedda and his ancestors.
- Phillimore 1888:164 — 816, the Annales Cambriae
- Reeves 1857:389, the Chronicon Hyense — year 816, "Conan mac Ruadhrach, rex Britonum, defunctus est"
- Phillimore 1888:164 — 818, the Annales Cambriae
- Davies, John (1990), A History of Wales (First ed.), London: Penguin Group (published 1993), ISBN 0-7139-9098-8
- Lloyd, John Edward (1911), A History of Wales from the Earliest Times to the Edwardian Conquest, I (2nd ed.), London: Longmans, Green, and Co (published 1912)
- Owen, Aneurin, ed. (1841), Ancient Laws and Institutes of Wales, I
- Parry, Henry (translator), ed. (1829), "Brut y Saeson", Archaeologia Cambrensis, Third, IX (XXXIII), London: J. Russell Smith (published 1863), p. 59–67
- Phillimore, Egerton, ed. (1887), "Pedigrees from Jesus College MS. 20", Y Cymmrodor, VIII, Honourable Society of Cymmrodorion, pp. 77–92
- Phillimore, Egerton (1888), "The Annales Cambriae and Old Welsh Genealogies, from Harleian MS. 3859", in Phillimore, Egerton, Y Cymmrodor, IX, Honourable Society of Cymmrodorion, pp. 141–183
- Reeves, William, ed. (1857), "Additional Notes (Chronicon Hyense)", The Life of St. Columba, to which are added Copious Notes and Dissertations, Dublin: Irish Archaeological and Celtic Society, pp. 369–413
- Skene, William Forbes, ed. (1867), Chronicles of the Picts, Chronicles of the Scots, and Other Early Memorials of Scottish History, Edinburgh: Edinburgh General Register House
Caradog ap Meirion
| King of Gwynedd
798 – 816
Hywel ap Rhodri Molwynog