Cognomen Yamasa (ヤマサ 
, Yamasa 
, ยามาสา ) , all over the world, is a rare family name. The last name Yamasa is characteristic of Thailand, where it is a rare surname, Philippines, where it is a very rare surname, and the United Kingdom, where it is an extremely rare surname. Measured by absolute frequency, the name is most common in Thailand, Philippines, and the United States. Also, Yamasa is the forename as well as the last name.