Globally, Kilja (Kilja 
, Киля 
) is a very rare principally female, but scarcely male forename. The first name Kilja is characteristic of Bulgaria, where it is a rare female name, Kazakhstan, and Russia, where it is a very rare female name. Not in comparison with a country's population, it is commonest in the United States, Kazakhstan, and Bulgaria. Much less frequently, Kilja is the last name as well as the forename.