Surname Koupai (Купай 
, Koupai 
) , in all the world, is a very rare last name. The cognomen Koupai is habitual in Kyrgyzstan, where it is a very rare surname, Russia, and Iran. Not in comparison with a country's population, it is the most numerous in Russia, Iran, and the United States. Very seldom, Koupai is the forename as well as the last name.