Cronn hi Cualngi: probably a hill or river of this name near Cualnge
Cruachan Ai: the ancient seat and royal burial-place of the kings of Connacht, ten miles north-east of the modern Rathcroghan, near Belanagare, in the County Roscommon (pronounced Croohan)
Cruinn: a river in Cualnge: probably the stream now called the Piedmont River, emptying into Dundalk Bay
Cruthnech: the land of the Irish Picts; the northern part of the County Down and the southern part of the County Antrim
Cu, Cucuc, Cuacain, Cucucan, Cucucuc: diminutives of the name Cuchulain
Cualnge: Cooley, a mountainous district between Dundalk Bay and Drogheda, in the barony of Lower Dundalk, in the County Louth. It originally extended to the County Down, and the name is now applied to the southern side of the Carlingford Mountains (pronounced Cūln'ya)
Cualu: a district in the County Wicklow
Cuchulain: the usual name of the hero Setanta; son of the god Lug and of Dechtire, and foster-son of Sualtaim (pronounced Cuhŭ́lin)
Cuib: on the road to Midluachair
Cuilenn: the Cully Waters flowing southward from County Armagh into County Louth