Cognomen Ясас (Jasas 
, Jasos 
, Iasas ) , throughout the world, is a rare surname. The last name Ясас is characteristic of Lithuania, where it is quite a common surname, Kuwait, where it is a rare surname, and Ireland. In absolute terms, it most frequently occurs in Lithuania, Russia, and the United States. Much less frequently, Ясас is the forename as well as the last name.