Family name ฤทธิสิทธิ์ (Power 
, ฤทธิสิทธิ์ 
, Ritthisit ) , all around the world, is a common surname. The family name ฤทธิสิทธิ์ is characteristic of Ireland, where it is a common surname, Guernsey, where it is quite a common surname, and Australia (explore the name in all countries). Measured by absolute frequency, it is the most numerous in the United States, the United Kingdom, and Canada. Very seldom, ฤทธิสิทธิ์ is the forename as well as the last name.