Surname Tretjaks (Третяк 
, Tretjaks 
) , around the world, is a common family name. The surname Tretjaks is characteristic of Ukraine, where it is quite a common surname, Belarus, where it is quite a rare surname, and Latvia. Measured by absolute frequency, it is the most numerous in Eastern Europe, particularly Ukraine, Russia, and Belarus.
| VARIANT | COUNTRY |
|---|---|
| Третяк | Kazakhstan, Russia, Belarus, Bulgaria, Ukraine |
| Tretjaks | Estonia, Latvia |