Last name サダオ (Sadao 
, サダオ ) , around the globe, is quite a common surname. The last name サダオ is characteristic of Japan, where it is quite a rare surname, Philippines, where it is a rare surname, and Thailand. Measured by absolute frequency, it is the most numerous in Japan, Philippines, and China. Much less frequently, サダオ is the forename as well as the last name.