Ōhara (大原町, Ōhara-chō) was a town located in Aida District, Okayama Prefecture, Japan. As of 2003, the town had an estimated population of 4,630 and a density of 84.99 persons per km². The total area was 54.48 km². On March 31, 2005, Ōhara, along with the towns of Mimasaka, Aida and Sakutō, the village of Higashiawakura (all from Aida District), and the town of Katsuta (from Katsuta District), was merged to create the city of Mimasaka.