Cognomen Рейдар (Reidar 
, Рейдар 
) , throughout the world, is a rare surname. The surname Рейдар is characteristic of Norway, where it is quite a rare surname, Austria, where it is a rare surname, and Spain. Measured by absolute frequency, it is commonest in Norway, Spain, and China. More frequently, Рейдар is the forename as well as the last name.