Cognomen Kirbaj (Кирбай 
, Kirbaj 
) , around the world, is a rare last name. The surname Kirbaj is characteristic of Belarus, where it is quite a rare surname, Russia, where it is a very rare surname, and Venezuela.
| VARIANT | COUNTRY |
|---|---|
| Кирбай | Kazakhstan, Russia, Ukraine, Belarus |
| Kirbaj | United States, Venezuela |