Soyō (蘇陽町; -machi) was a town located in Aso District, Kumamoto, Japan.
On February 11, 2005 Soyō was merged with the town of Yabe, and the village of Seiwa, both from Kamimashiki District, to form the new town of Yamato and no longer exists as an independent municipality.
As of 2003, the town had an estimated population of 4,506 and a density of 37.89 persons per km². The total area was 118.92 km².