| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| Jokin | - | Basque | ||
| Jon (1) | YOON (Swedish, Norwegian), YON (Danish, Basque) | Swedish, Norwegian, Danish, Basque | ||
| Jone (1) | - | Basque | ||
| Joseba | - | Basque | ||
| Josepe | - | Basque | ||
| Josu | - | Basque | ||
| Josune | - | Basque | ||
| Julen | - | Basque | ||
| Katalin | KAWT-aw-leen (Hungarian) | Hungarian, Basque | ||
| Kattalin | - | Basque | ||
| Kemen | - | Basque | ||
| Kepa | - | Basque | ||
| Kerman | - | Basque | ||
| KistiÑE | - | Basque | ||
| Koldo | - | Basque |