| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| Kostandin | - | Albanian | ||
| Kostya | - | Russian | ||
| Kostyantyn | - | Ukrainian | ||
| Kotone | ko-to-ne | Japanese | ||
| Kotryna | - | Lithuanian | ||
| Kouki | ko:-kee | Japanese | ||
| Kouta | ko:-tah | Japanese | ||
| Krasimir | - | Bulgarian, Medieval Slavic | ||
| Krasimira | - | Bulgarian | ||
| Krastio | - | Bulgarian | ||
| Krastyo | - | Bulgarian | ||
| Krastyu | - | Bulgarian | ||
| KreŠImir | - | Croatian | ||
| KreŠImira | - | Croatian | ||
| KreŠO | - | Croatian |