C
- (Roscommon) Crossna
- (Mayo County) Crossboyne
- (Mayo County) Cross
- (Roscommon) Croghan
- (Mayo County) Crockets Town
- (County Galway) Croaghnakeela Island
- (Roscommon) Creggs
- (Mayo County) Cregganbaun
- (Mayo County) Creevy
- (Mayo County) Creevagh
- (Roscommon) Creeharmore
- (County Galway) Creduff
- (Roscommon) Crannagh
- (County Galway) Costelloe
- (Mayo County) Corroy
- (County Leitrim) Corrigo
- (County Leitrim) Corrawaleen
- (Mayo County) Corraun
- (Mayo County) Corraun
- (Mayo County) Corradrishy
- (County Galway) Cornamona
- (County Leitrim) Cornageeha
- (Roscommon) Cornafulla
- (County Leitrim) Corglass
- (Sligo) Corbally
- (County Galway) Coolagh
- (County Galway) Coolacurn
- (Sligo) Coola Cross Roads
- (Sligo) Coney Island
- (County Galway) Colmanstown