| Isidoro | | ee-see-DHO-ro (Spanish), ee-zee-DO-ro (Italian) | Spanish, Italian | |
| Isidro | | - | Spanish | |
| Isingoma | | - | Eastern African, Ganda | |
| Iskandar | | - | Arabic, Indonesian, Malay | |
| Iskra | | - | Bulgarian, Macedonian, Croatian, Serbian | |
| Isla | | IE-lə | Scottish | |
| Islay | | IE-lə | Scottish | |
| Islwyn | | - | Welsh | |
| Ismael | | - | Spanish, Biblical Greek | |
| Ismo | | EES-mo | Finnish | |
| Isobel | | - | Scottish | |
| 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 | |