Ōōso (汪応祖) was a local ruler of Okinawa Island, who was given the title of King of Sannan. He first contacted the Chinese emperor in 1403, claiming himself to be a younger brother or cousin of Shōsatto, the late King of Sannan, who reportedly had no son. Ōōso was given the title in the next year. His last contact was of 1413. In 1415, Taromai, who styled himself Crown Prince, reported Ōōso's death. He claimed that Ōōso was killed by his elder brother Tabuchi, who had in turn been killed by local chiefs, in favor of Crown Prince Taromai.