Surname Kostach (Kostach 
, Косташ 
) , around the globe, is quite a rare family name. The last name Kostach is characteristic of Eastern Europe, particularly Ukraine, where it is quite a rare surname, Russia, where it is a rare surname, and Belarus. In absolute terms, it is commonest in Ukraine, Russia, and Kazakhstan.
| VARIANT | COUNTRY |
|---|---|
| Kostach | Canada |
| Косташ | Russia, Kazakhstan, Ukraine, Kyrgyzstan, Belarus |