Last name Oai (Oai 
, Оай 
, Ouaï) , around the world, is a rare cognomen. The family name Oai is habitual in Vietnam, where it is a rare surname, Malaysia, and Australia, where it is a very rare surname. Not in comparison with a country's population, it is commonest in Vietnam, China, and Malaysia. Likewise, Oai is the forename as well as the last name.