| Julija | | YOO-lee-yah (Slovene) | Slovene, Croatian, Lithuanian | |
| Julijana | | - | Slovene, Croatian, Serbian, Macedonian | |
| Juraj | | YOO-rahy (Croatian) | Croatian, Slovak | |
| Jure | | - | Slovene, Croatian | |
| Jurica | | - | Croatian, Slovene | |
| Juro (1) | | - | Croatian | |
| Kaneonuskatew | | - | Native American, Cree | |
| Karla | | KAHR-lah (German) | German, Swedish, Norwegian, Danish, Croatian | |
| Karlo | | KAHR-lo | Croatian | |
| Karmela | | - | Croatian | |
| Karmen | | - | Slovene, Croatian | |
| Karolina | | kah-raw-LEE-nah (Polish), kah-ro-LEE-nah (Swedish, German) | Polish, Swedish, Norwegian, Danish, Hungarian, Slovene, Croatian, Macedonian, Lithuanian, German | |
| Kata | | KAH-tah (Finnish) | Hungarian, Finnish, Croatian | |
| Katarina | | kah-tah-REE-nah (German, Swedish) | German, Swedish, Norwegian, Danish, Hungarian, Croatian, Serbian, Slovene | |
| Kate | | KAYT (English) | English, Croatian | |