Surname Isao (功 
, Isao 
, イサオ ) , in the world, is a common cognomen. The cognomen Isao is habitual in Eastern Asia, particularly Japan, where it is quite a common surname, Taiwan, where it is quite a rare surname, and China. Not in comparison with a country's population, it is the most numerous in Japan, China, and Philippines. Also, Isao is the forename as well as the last name.