| Katica | | - | Croatian, Slovene, Hungarian | |
| Kawacatoose | | - | Native American, Cree | |
| Kisecawchuck | | - | Native American, Cree | |
| Klara | | KLAH-rah (German, Russian, Polish) | Swedish, Norwegian, Danish, Icelandic, German, Russian, Ukrainian, Polish, Slovene, Croatian | |
| Klaudija | | - | Croatian | |
| Klaudio | | - | Croatian | |
| Klementina | | - | Slovene, Croatian | |
| Koraljka | | - | Croatian | |
| Kornelija | | - | Croatian, Serbian | |
| KreŠImir | | - | Croatian | |
| KreŠImira | | - | Croatian | |
| KreŠO | | - | Croatian | |
| Kristijan | | KREES-tee-yahn (Serbian, Croatian) | Serbian, Croatian, Slovene, Macedonian | |
| Kristina | | kris-TEE-nah (German) | Swedish, Norwegian, Danish, Russian, German, Slovene, Czech, Lithuanian, Serbian, Croatian, Faroese, | |
| Kristofor | | - | Croatian (Rare) | |