| Iseult | | i-SOOLT (English), i-ZOOLT (English), EE-səlt (English) | Arthurian Romance | |
| Isidorus | | - | Late Roman | |
| Isolda | | i-ZOL-də (English), i-SOL-də (English) | Arthurian Romance | |
| Isolde | | i-ZOL-də (English), i-SOL-də (English), ee-ZAWL-du (German) | English (Rare), German, Arthurian Romance | |
| Italus | | - | Roman Mythology | |
| Iucunda | | - | Late Roman | |
| Iulia | | YOO:-li-a (Ancient Roman) | Romanian, Ancient Roman | |
| Iulian | | - | Romanian | |
| Iuliana | | - | Romanian, Ancient Roman | |
| Iulianus | | - | Ancient Roman | |
| Iuliu | | - | Romanian | |
| Iulius | | YOO:-li-uws | Ancient Roman | |
| Iunia | | - | Ancient Roman, Biblical Latin | |
| Iunius | | - | Ancient Roman | |
| Iuno | | - | Roman Mythology | |