| Catrin | Woman | Welsh Names |
| Ceinwen | Woman | Welsh Names |
| Celyn | Unisex | Welsh Names |
| Ceri | Unisex | Welsh Names |
| Ceridwen | Woman | Welsh Names |
| Ceron | Man | Welsh Names |
| Cerys | Woman | Welsh Names |
| Cledwyn | Man | Welsh Names |
| Collen | Man | Welsh Names |
| Colwyn | Unisex | Welsh Names |
| Crwys | Unisex | Welsh Names |
| Dafydd | Man | Welsh Names |
| Dai | Man | Welsh Names |
| Delyth | Woman | Welsh Names |
| Derwyn | Man | Welsh Names |
| Dewey | Man | Welsh Names |
| Dewi | Man | Welsh Names |
| Dillan | Man | Welsh Names |
| Dillon | Man | Welsh Names |
| Dilwyn | Man | Welsh Names |