| Ciaran | Man | Irish Names |
| Cillian | Man | Irish Names |
| Ciniod | Man | Irish Names |
| Clancy | Man | Irish Names |
| Clidhna | Woman | Irish Names |
| Cliona | Woman | Irish Names |
| Clodagh | Woman | Irish Names |
| Coffey | Unisex | Irish Names |
| Colm | Man | Irish Names |
| Colum | Man | Irish Names |
| Comiskey | Unisex | Irish Names |
| Conan | Man | Irish Names |
| Conary | Unisex | Irish Names |
| Conlan | Man | Irish Names |
| Conleth | Unisex | Irish Names |
| Conley | Man | Irish Names |
| Connell | Man | Irish Names |
| Conner | Man | Irish Names |
| Connery | Unisex | Irish Names |
| Connley | Man | Irish Names |