| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| CillÍN | - | Irish | ||
| Cillian | - | Irish | ||
| CinÁEd | KIN-ahj (Irish) | Scottish, Irish | ||
| Cionaodh | KIN-eech | Irish | ||
| ClÍDna | - | Irish Mythology | ||
| ClÍOdhna | KLEE-u-na | Irish, Irish Mythology | ||
| ClÍOna | - | Irish | ||
| Clancy | KLANT-see | Irish, English (Rare) | ||
| Cleena | - | Irish | ||
| Clodagh | - | Irish | ||
| Cody | KO-dee | English, Irish | ||
| Coilean | - | Irish | ||
| Coleman | - | English, Irish | ||
| Colin (1) | KAHL-in (Scottish, Irish, English), KOL-in (English) | Scottish, Irish, English | ||
| Colm | - | Irish |