| Casimiro | | - | Spanish, Portuguese, Italian | |
| Caspar | | - | Judeo-Christian Legend | |
| Casper | | KAHS-pər (Dutch) | Dutch, Swedish, Norwegian, Danish | |
| Cass | | KAS | English | |
| Cassandra | | kə-SAN-drə (English), kə-SAHN-drə (English), kahs-SAHN-drah (Italian) | English, Spanish, Portuguese, Italian, French, German, Greek Mythology (Latinized) | |
| Cassarah | | kə-SER-ə, KAS-ə-rə | English (Rare) | |
| Cassidy | | KAS-i-dee | English (Modern) | |
| Cassie | | KAS-ee | English | |
| Cassius | | KASH-əs (English), KAS-ee-əs (English) | Ancient Roman, English | |
| Catahecassa | | - | Native American, Shawnee | |
| Catalina | | kah-tah-LEE-nah | Spanish | |
| Catarina | | kah-tah-REE-nah (Italian), ka-ta-REE-na (Galician) | Italian, Portuguese, Occitan, Galician | |
| Cate | | KAYT | English (Rare) | |
| CathÁN | | - | Irish | |
| Cathair | | KA-heer | Irish | |