| Ismene | | - | Greek Mythology | |
| Isocrates | | - | Ancient Greek (Latinized) | |
| Isokrates | | - | Ancient Greek | |
| Israel | | IZ-ray-əl (English), IZ-ree-əl (English) | Jewish, English, Biblical, Biblical Greek | |
| Ithamar | | - | Biblical, Biblical Latin, Biblical Greek | |
| Jason | | JAY-sən (English) | English, French, Greek Mythology (Anglicized), Biblical | |
| Jocasta | | jo-KAS-tə (English) | Greek Mythology (Latinized) | |
| Kadmos | | - | Greek Mythology | |
| Kain | | - | Biblical Greek | |
| Kainan | | - | Biblical Greek | |
| Kallias | | - | Ancient Greek | |
| Kallikrates | | - | Ancient Greek | |
| Kalliope | | - | Greek Mythology | |
| Kallisto | | - | Greek Mythology, Ancient Greek | |
| Kallistos | | - | Ancient Greek | |