Surname 恒川 (恒川 
, Hengchuan 
, Tsunekawa 
) , around the world, is a rare last name. The surname 恒川 is characteristic of Japan, where it is a very rare surname, Chile, and Thailand. Measured by absolute frequency, it is the most numerous in China, Japan, and the United States. More frequently, 恒川 is the forename as well as the last name.