| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 261 | Connell | Celtic | Strong in battle. | M | |
| 262 | Connla | Celtic | Mythical son of Conn. | M | |
| 263 | Conroy | Celtic | Persistent. | M | |
| 264 | Conway | Celtic | Hound of the plain. | M | |
| 265 | Corann | Celtic | Mythical druid. | M | |
| 266 | Cordelia | Celtic | Of the sea. | F | |
| 267 | Cormac | Celtic | Charioteer. | M | |
| 268 | Coventina | Celtic | Water goddess. | F | |
| 269 | Cradawg | Celtic | Mythical son of Bran. | M | |
| 270 | Cuchulain | Celtic | Mythical Hound of Ulster. | M | |
| 271 | Cuinn | Celtic | Wise. | M | |
| 272 | Culain | Celtic | Mythical smith. | M | |
| 273 | Culann | Celtic | Mythical smith. | M | |
| 274 | Cullen | Celtic | Cub. | M | |
| 275 | Custennin | Celtic | Mythical giant. | M | |
| 276 | Dallas | Celtic | Dwells by the waterfall. | M | |
| 277 | Daman | Celtic | Demon. | M | |
| 278 | Dana | Celtic | From Denmark. Dana was the Celtic goddess of fertility. | F | |
| 279 | Darcy | Celtic | Dark. | M | |
| 280 | Dearg | Celtic | Son of Daghda. | M | |