Family name 水内 (Mizuuchi 
, 水内 , Mizuuti ) , all over the world, is a very rare last name. The family name 水内 is characteristic of the United States, where it is an extremely rare surname, South Africa, and Brazil. Not in comparison with a country's population, it is commonest in the United States, China, and Brazil. More frequently, 水内 is the forename as well as the last name.