| Kalin | | - | Bulgarian | |
| Kalina | | - | Bulgarian, Macedonian, Polish | |
| Kaloyan | | - | Bulgarian | |
| Kamen | | - | Bulgarian | |
| Katerina | | - | Macedonian, Russian, Bulgarian, Greek, Late Roman | |
| Kiril | | - | Bulgarian, Macedonian | |
| Klavdiya | | KLAHV-dee-yah (Russian) | Russian, Ukrainian, Bulgarian | |
| Kliment | | klee-MYENT (Russian) | Russian, Ukrainian, Bulgarian, Macedonian | |
| Konstantin | | KAWN-stahn-teen (German), kahn-stahn-TEEN (Russian) | German, Hungarian, Russian, Serbian, Bulgarian, Macedonian | |
| Kosta | | - | Bulgarian | |
| Kostadin | | - | Bulgarian, Macedonian | |
| Krasimir | | - | Bulgarian, Medieval Slavic | |
| Krasimira | | - | Bulgarian | |
| Krastio | | - | Bulgarian | |
| Krastyo | | - | Bulgarian | |