| Name | Meaning | Gender | Origin |
|---|
| Irma | universal, complete | Female | |
| Isabella | pledged to God | Female | Spanish |
| Isis | throne | Female | Egyptian |
| Isolda | Rule of ice
| Female | |
| Ivy | ivy plant, a wine | Female | Plant |
| Jacinda | Beautiful
| Female | English |
| Jackie | supplanter | Female | English |
| Jacynth | Beautiful, Beloved
| Female | |
| James Potter | Harry's father who was killed by Lord Voldemort.
| Male | |
| Javiero | Born in January
| Male | |
| Jekyl | | Male | |
| Jeremias | Exalted of the Lord
| Male | |
| Jewel | Jewel
| Female | Word |
| Jimena | Heard
| Female | Spanish |
| Jinx | Charm, Spell | Female | Latin |
| Jock | God has been gracious: has shown favor. Based on John or Jacques.
| Male | Scottish |
| Johnston | From John's farm
| Male | |
| Jordan | The descending river, to flow | Male | Hebrew |
| Jorge | Spanish form of George farmer
| Male | Spanish |
| Joy | From Joyce - Gay and joyful | Female | Word |
| Julie | Youthful: Jove's child. A feminine of Julian.
| Female | |
| Juliette | youthful | Female | |
| Jupiter | Zeus, Father | Male | Roman |
| Kai | Fire
| Male | Hawaiian |
| Kali | after the Indian goddess of death | Female | Sanskrit |