Cognomen Vasilius (Vasilius 
, Василюс 
) , worldwide, is a rare family name. The cognomen Vasilius is habitual in Lithuania, where it is quite a rare surname, Belarus, where it is a rare surname, and Kyrgyzstan, where it is a very rare surname. Not in comparison with a country's population, it most frequently occurs in Lithuania, Russia, and Belarus. Much less frequently, Vasilius is the forename as well as the last name.