Cognomen Postoian (Постоян 
, Postoian 
) , across the world, is a rare last name. The family name Postoian is characteristic of Ukraine, where it is a rare surname, Russia, where it is a very rare surname, and Georgia. Not in comparison with a country's population, it most frequently occurs in Ukraine, Russia, and the United States. Very seldom, Postoian is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Постоян | Russia, Ukraine, Armenia |
| Postoian | United States, Canada, Georgia |