The Okayama Domain (岡山藩 Okayama han?) was a Japanese domain of the Edo period. It was associated with Bizen Province in modern-day Okayama Prefecture.
In the han system, Okayama was a political and economic abstraction based on periodic cadastral surveys and projected agricultural yields. In other words, the domain was defined in terms of kokudaka, not land area. This was different from the feudalism of the West.
The domain sided with the Kyoto government during the Boshin War.
The hereditary daimyo were head of the clan and head of the domain.