Cognomen Oslaj (Oslaj 
) , worldwide, is a rare surname. The last name Oslaj is habitual in Slovenia, where it is quite a rare surname, Poland, where it is a very rare surname, and France. Not in comparison with a country's population, this name is the most popular in Slovenia, Brazil, and Poland. Very seldom, Oslaj is the forename as well as the last name.