Surname Koulnis (Koulnis 
, Кульнис 
) , across the world, is a very rare last name. The family name Koulnis is habitual in Belarus, where it is a rare surname, Russia, where it is a very rare surname, and the United States, where it is an extremely rare surname.
| VARIANT | COUNTRY |
|---|---|
| Koulnis | United States |
| Кульнис | Belarus, Russia |