Surname ريدار (Reidar 
, ريدار 
) , in the world, is a rare cognomen. The cognomen ريدار 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, ريدار is the forename as well as the last name.