The Mihara Domain (三原藩, Mihara-han) was a feudal domain of Japan in the Edo period. Located in what is now Mihara City, Hiroshima Prefecture, it encompassed the southern part of Bingo Province. Its headquarter was Mihara Castle (三原城 Mihara-jō). At its peak, it was rated at 30,000 koku. For more than two hundred years the daimyō of Mihara were a collateral branch of the Asano clan who held Hiroshima Domain. It was a subordinate of Hiroshima Domain where the main line of the Asano clan ruled from.