| Isokrates | | - | Ancient Greek | |
| Ivo (1) | | EE-vo (German, Dutch, Italian), EE-fo (German), EE-voo (Portuguese) | German, Dutch, Italian, Portuguese, Czech, Ancient Germanic | |
| Jordanes | | - | Ancient Germanic | |
| Judda | | - | Ancient Germanic | |
| Kallias | | - | Ancient Greek | |
| Kallikrates | | - | Ancient Greek | |
| Kallisto | | - | Greek Mythology, Ancient Greek | |
| Kallistos | | - | Ancient Greek | |
| Kallistrate | | - | Ancient Greek | |
| Karl | | KAHRL (German, Danish, English, Finnish) | German, Swedish, Norwegian, Danish, English, Finnish, Ancient Germanic | |
| Karpos | | - | Ancient Greek, Biblical Greek | |
| Kassandra | | kə-SAN-drə (English) | Greek Mythology, Ancient Greek, English (Modern) | |
| Kassandros | | - | Ancient Greek | |
| Kleisthenes | | - | Ancient Greek | |
| Kleitos | | - | Ancient Greek | |