| Irina | | ee-REE-nah (Russian), EE-ree-nah (Finnish) | Russian, Bulgarian, Macedonian, Romanian, Finnish, Georgian | |
| Isaija | | - | Serbian, Macedonian | |
| Isidor | | EE-see-dawr (German) | German, Russian, Macedonian | |
| Isidora | | ee-see-DHO-rah (Spanish), ee-zee-DO-rah (Italian), iz-i-DAWR-ə (English) | Serbian, Macedonian, Spanish, Portuguese, Russian (Rare), Italian (Rare), English (Rare), Ancient Gr | |
| Iskra | | - | Bulgarian, Macedonian, Croatian, Serbian | |
| Iva (1) | | - | Bulgarian, Serbian, Croatian, Macedonian | |
| Ivan | | ee-VAHN (Russian, Ukrainian), IE-vən (English) | Russian, Bulgarian, Ukrainian, Belarusian, Serbian, Croatian, Czech, Slovak, Macedonian, Slovene, En | |
| Ivana | | - | Czech, Slovak, Serbian, Croatian, Slovene, Bulgarian, Macedonian | |
| Ivo (2) | | - | Bulgarian, Serbian, Croatian, Macedonian | |
| Ivona | | - | Czech, Slovak, Croatian, Macedonian | |
| Jaga | | - | Croatian, Serbian, Macedonian | |
| Jagoda | | yah-GAW-dah (Polish) | Croatian, Serbian, Macedonian, Polish | |
| Jakov | | - | Serbian, Croatian, Macedonian | |
| Jasmina | | - | Croatian, Serbian, Slovene, Macedonian | |
| Jasna | | - | Croatian, Serbian, Slovene, Macedonian | |