Cognomen Ямагучи (Yamaguchi 
, Ямагучи 
, Iamaguchi ) , all over the world, is a common family name. The cognomen Ямагучи is characteristic of British Virgin Islands, where it is quite a common surname, Bahamas, where it is quite a rare surname, and Japan. In absolute terms, it most frequently occurs in Japan, Brazil, and the United States. Very seldom, Ямагучи is the forename as well as the last name.