Cognomen Bilej (Bilej 
, Билей 
) , all around the world, is a rare last name. The cognomen Bilej is habitual in Czechia, where it is a rare surname, Kazakhstan, and Belarus. Not in comparison with a country's population, it is the most numerous in Russia, Czechia, and Kazakhstan. Very seldom, Bilej is the forename as well as the last name.