| Caspian | Man | English Names |
| Cassander | Man | Greek Names |
| Cassandra | Woman | Greek Names |
| Cassara | Woman | American Names |
| Cassia | Woman | Greek Names |
| Cassian | Man | Latin Names |
| Cassidy | Unisex | Irish Names |
| Cassie | Woman | English Names |
| Cassiopeia | Woman | Greek Names |
| Cassius | Man | Latin Names |
| Casta | Man | Spanish Names |
| Castalia | Woman | Greek Names |
| Castañeda | Unisex | Spanish Names |
| Castel | Unisex | Spanish Names |
| Castellana | Woman | Latin Names |
| Castiel | Unisex | Latin Names |
| Castillo | Unisex | Spanish Names |
| Castimir | Man | Slavic Names |
| Castor | Man | Greek Names |
| Castrello | Man | Spanish Names |