Mimasaka is a city located in Okayama Prefecture, Japan. As of 31 January 2023, the city had an estimated population of 25,946 in 12287 households and a population density of 60 persons per km2. The total area of the city is 429.29 square kilometres (165.75 sq mi).

Okayama Prefecture is a prefecture of Japan located in the Chūgoku region of Honshu. Okayama Prefecture has a population of 1,906,464 and has a geographic area of 7,114 km2. Okayama Prefecture borders Tottori Prefecture to the north, Hyōgo Prefecture to the east, and Hiroshima Prefecture to the west.