| Isidore | | IZ-i-dawr (English), ee-zee-DOR (French) | English, French, Georgian, Jewish | |
| Isidoros | | - | Ancient Greek | |
| Isis | | IE-sis (English) | Egyptian Mythology (Hellenized) | |
| Islambek | | - | Chechen | |
| Isocrates | | - | Ancient Greek (Latinized) | |
| Isokrates | | - | Ancient Greek | |
| Isolde | | i-ZOL-də (English), i-SOL-də (English), ee-ZAWL-du (German) | English (Rare), German, Arthurian Romance | |
| Israel | | IZ-ray-əl (English), IZ-ree-əl (English) | Jewish, English, Biblical, Biblical Greek | |
| Israfil | | - | Judeo-Christian Legend | |
| Issac | | IE-zək | English | |
| Issy | | - | English | |
| Iudicael | | - | Ancient Celtic | |
| Iudocus | | - | Ancient Celtic (Latinized) | |
| Iulia | | YOO:-li-a (Ancient Roman) | Romanian, Ancient Roman | |
| Iuliana | | - | Romanian, Ancient Roman | |