| Name | Meaning | Gender | Origin |
|---|
| Jo | Variation of Johanna, God is gracious | Female | English |
| Joe Cool | | Unisex | Hebrew |
| Joely | French, pretty | Female | Feminine |
| Jolly | Full of good humor and high spirits. | Unisex | |
| Jonesy | | Unisex | Hebrew |
| Josette | Jehovah increases | Female | |
| Joy | From Joyce - Gay and joyful | Female | Word |
| Juggernaut | | Unisex | Hebrew |
| Juju | | Unisex | Hebrew |
| Julie | Youthful: Jove's child. A feminine of Julian.
| Female | |
| Juliette | youthful | Female | |
| Jumpy | | Unisex | Hebrew |
| Juniper | Juniper Tree | Female | English |
| Juno | queen of the heavens | Female | Latin |
| Just | | Unisex | Hebrew |
| Jynx | Charm, Spell | Unisex | Latin |
| Kahlua | | Unisex | |
| Kahuna | | Unisex | |
| Kaiser | Any of the emperors of The Holy Roman Empire, Austria or Germany | Unisex | |
| Kalamazoo | | Unisex | |
| Kali | after the Indian goddess of death | Female | Sanskrit |
| Kannika | Japanese for jasmine like blossom | Unisex | |
| Karen | pure | Female | Danish |
| Karma | Fate or destiny (Hinduism and Buddhism) | Female | Hindi |
| Kasha | | Unisex | Hebrew |