| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| Carroll | - | Irish | ||
| Casey | KAY-see | English, Irish | ||
| CathÁN | - | Irish | ||
| Cathair | KA-heer | Irish | ||
| Cathal | KA-hal | Irish | ||
| Cathaoir | KA-heer | Irish | ||
| Cathasach | - | Ancient Irish | ||
| Cathleen | kath-LEEN | Irish, English | ||
| Catrina | - | Irish, Scottish | ||
| Catriona | ka-TREE-na, ka-TREE-o-na | Irish, Scottish | ||
| Ceallach | KEL-akh | Irish | ||
| CeallachÁN | - | Irish | ||
| Ceallagh | - | Irish | ||
| Cearbhall | - | Irish | ||
| CennÉTig | - | Irish |