C
- (Mayo County) Claggan
- (Mayo County) Castleaffy
- (Mayo County) Carrickawart Island
- (Mayo County) Carrowcally
- (Mayo County) Corillan
- (Mayo County) Camel Island
- (Mayo County) Cahergal
- (Mayo County) Cloonfohler
- (Mayo County) Callowbrack
- (Mayo County) Camcloon
- (Mayo County) Cushinkeel
- (Mayo County) Cloonfert
- (Mayo County) Cregganbell
- (Mayo County) Cloonsunna
- (Mayo County) Creeragh
- (Mayo County) Cloondeash
- (Mayo County) Cloonshinnagh
- (Mayo County) Cock Island
- (Mayo County) Cornanool
- (Mayo County) Carha
- (Mayo County) Cummer
- (Mayo County) Carrownaclea
- (Mayo County) Cuiltrean
- (Mayo County) Coarse Island
- (Mayo County) Curraghmore
- (Mayo County) Craggagh
- (Mayo County) Corskeagh
- (Mayo County) Carrowgarve
- (Mayo County) Coolaghbaun
- (Mayo County) Conrea