Surname Ouaï (Oai 
, Ouaï, Uaio) , around the world, is a rare last name. The last name Ouaï is habitual in Vietnam, where it is a rare surname, Malaysia, and Australia, where it is a very rare surname. Measured by absolute frequency, it most frequently occurs in Vietnam, China, and Malaysia. Likewise, Ouaï is the forename as well as the last name.