| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 241 | Cedric | Celtic | Cbief. | M | |
| 242 | Celyddon | Celtic | Mythical father of Culhwch. | M | |
| 243 | Chad | Celtic | Defence. | M | |
| 244 | Cinnia | Celtic | Beauty. | F | |
| 245 | Cinnie | Celtic | Beauty. | F | |
| 246 | Clust | Celtic | Mythical son of Clustfeinad. | M | |
| 247 | Clustfeinad | Celtic | Mythical father of Clust. | M | |
| 248 | Cocidius | Celtic | Mythical hunter god. | M | |
| 249 | Coinneach | Celtic | Handsome. | M | |
| 250 | Con | Celtic | Wise. | M | |
| 251 | Conal | Celtic | High; mighty. | M | |
| 252 | Conall | Celtic | Strong in battle High; mighty. | M | |
| 253 | Conall Cernach | Celtic | Mythical Ulster chieftain. | M | |
| 254 | Conan | Celtic | High, wise. Introduced into Britain after the Norman Conquest. Famous bearers: Sir Arthur Conan Doyle, creator of the detective Sherlock Holmes; a number of counts and dukes of Brittany bore the name Conan. | M | |
| 255 | Conant | Celtic | Wise. | M | |
| 256 | Conchobar | Celtic | Mythical hero. | M | |
| 257 | Condan | Celtic | Dark haired wise man. | M | |
| 258 | Condon | Celtic | Dark haired wise man. | M | |
| 259 | Conn | Celtic | Mythical son of Lir: wise; High; mighty. | M | |
| 260 | Connal | Celtic | 'High; mighty.'. | M | |