Cognomen Kostyu (Kostyu 
, Костю 
) , in all the world, is a rare last name. The cognomen Kostyu is habitual in Eastern Europe, particularly Hungary, where it is quite a rare surname, Ukraine, where it is a rare surname, and Russia, where it is a very rare surname.
| VARIANT | COUNTRY |
|---|---|
| Kostyu | Ukraine, United States, Hungary |
| Костю | Russia, Ukraine |