Ryūō (竜王町 Ryūō-machi) was a town located in Nakakoma District, Yamanashi, Japan.
On September 1, 2004 Ryūō was merged with the town of Futaba, from Kitakoma District, and the town of Shikishima, from Nakakoma District, to form the new city of Kai.
As of 2003, the town had an estimated population of 40,969 and a density of 3,200.70 persons per km². The total area was 12.80 km².