Carn macBuachalla, at Dunseverick, in Ulster
Carbre: stepson of Conchobar and brother of Ailill
Carrloeg: a place in Ulster
Casruba: father of Lugaid and grandfather of Dubthach
Cathba: north-east of Ochonn, in Meath; or a river flowing into the Boyne, some distance to the west of Slane
Cathba: a druid of Conchobar's court; according to some accounts, the natural father of King Conchobar (pronounced Cahvah)
Celtchar: son of Uthechar, an Ulster warrior
Cenannas na rig: Kells, in the Covinty Meath
Cenn Abrat: a range of hills on the borders of the Counties Cork and Limerick
Cet macMagach: a Connacht warrior