Diarmait mac Ruadrach
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About
Diarmait mac Ruadrach, King of Airthir Liphi - the eastern Liffey plain around Naas - died in 832, a king of the first Viking generation: the longships were in the Liffey and on the coasts throughout his reign, and the raids on the great monasteries had begun. The dynasty bent, endured, and kept the kingship - as it would for two more centuries.
Research notes
✓ DOCUMENTED (Source: the Uí Fáeláin / Uí Dúnlainge royal genealogy of Leinster, attested in the Irish Annals and the medieval tracts (Book of Leinster; Rawlinson B502 - Genelach h-Úa n-Dúnlainge); supplied 23 Jul 2026.): DIARMAIT MAC RUADRACH, KING OF LEINSTER; d. 832. Father of Muirecan. Direct ancestor. Added 23 Jul 2026. ||TITLE CORRECTED 9 Oct 2026|| Annals style him King of AIRTHIR LIPHI (AU obit 832), not King of Leinster - that was his brother Muiredach mac Ruadrach (d.829). Prose adjusted. ⚠ SAME-NAME TRAP, banked: genealogy sites propose this Diarmait as father of CAIRPRE MAC DIARMATA d.876 of the Ui Cheinnselaig (I100821) - WRONG: he is Ui Faelain of Naas, the Genelach's name there is Rudgal not Ruadrach, and his own pedigree is fully accounted for here. Do not graft; see the frontier note on I100821.