| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| 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 | ||
| ColmÁN | - | Irish | ||
| Colum | - | Irish | ||
| Columban | kə-LUM-bən (English) | Irish | ||
| Comgal | - | Irish | ||
| Comgall | - | Irish |