| Justyna | | yuws-TI-nah | Polish | |
| Kacper | | KAHTS-per | Polish | |
| Kaja (2) | | KIE-ah (Polish) | Polish, Slovene | |
| Kajetan | | kah-YE-tahn | Polish | |
| Kalina | | - | Bulgarian, Macedonian, Polish | |
| Kamil (2) | | KAH-meel (Polish) | Czech, Slovak, Polish | |
| Kamila | | kah-MI-lah (Czech, Slovak), kah-MEE-lah (Polish) | Czech, Slovak, Polish | |
| Karina | | kah-REE-nah (Swedish, Polish, German, Russian), kə-REE-nə (English) | Swedish, Danish, Norwegian, Polish, German, Russian, English | |
| Karol | | KAH-rawl (Polish) | Polish, Slovak, Slovene | |
| Karolina | | kah-raw-LEE-nah (Polish), kah-ro-LEE-nah (Swedish, German) | Polish, Swedish, Norwegian, Danish, Hungarian, Slovene, Croatian, Macedonian, Lithuanian, German | |
| Kasandra | | kə-SAN-drə (English) | English (Modern), Polish | |
| Kasia | | KAH-shah | Polish | |
| Kasper | | KAHS-per (Polish, Swedish), KAHS-pər (Dutch) | Polish, Dutch, Swedish, Norwegian, Danish | |
| Katarzyna | | kah-tah-ZHI-nah | Polish | |
| Kazia | | KAH-zhah | Polish | |