Okayama Domain was a feudal domain under the Tokugawa shogunate of Edo period Japan, in what is now eastern Okayama Prefecture on the island of Honshu. It controlled all of Bizen Province and a small portion of Bitchū Province was centered around Okayama Castle, and was ruled throughout its history by a branch of the Ikeda clan. Okayama Domain was dissolved in the abolition of the han system in 1871 and is now part of Okayama Prefecture. Okayama Domain had two sub-domains, Kamogata Domain (鴨方藩) and Ikusaka Domain (生坂藩). In addition, six of the clans who served as hereditary karō of the domain had kokudaka equivalents to that of daimyō.

Bizen Province was a province of Japan in the area that is eastern Okayama Prefecture in the Chūgoku region of western Japan. Bizen bordered Bitchū, Mimasaka, and Harima Provinces. Its abbreviated form name was Bishū (備州). In terms of the Gokishichidō system, Bizen was one of the provinces of the San'yō circuit. Under the Engishiki classification system, Bizen was ranked as one of the 35 "superior countries" (上国) in terms of importance, and one of the "near countries" (近国) in terms of distance from the capital. The provincial capital was located in what is now the city of Okayama.