Ōnan is a town located in Ōchi District, Shimane Prefecture, Japan. As of 31 July 2023, the town had an estimated population of 9,838 in 4712 households and a population density of 23 persons per km². The total area of the town is 419.29 square kilometres (161.89 sq mi).

Shimane Prefecture is a prefecture of Japan located in the Chūgoku region of Honshu. Shimane Prefecture is the second-least populous prefecture of Japan at 665,205 and has a geographic area of 6,708.26 km2. Shimane Prefecture borders Yamaguchi Prefecture to the southwest, Hiroshima Prefecture to the south, and Tottori Prefecture to the east.