| Native Name: | 生実藩 |
| Conventional Long Name: | Oyumi Domain |
| Common Name: | Oyumi Domain |
| Subdivision: | Han |
| Status Text: | under Tokugawa shogunate Japan |
| Government Type: | Daimyō |
| Today: | part of Chiba Prefecture |
| Year Start: | 1623 |
| Year End: | 1871 |
| Era: | Edo period |
was a Japanese domain of the Edo period, located in Shimōsa Province (modern-day Chiba Prefecture), Japan. The site of the Oyumi jin'ya is now under a residential area of the city of Chiba. The domain was ruled through its entire history by the Morikawa clan.
Oyumi Domain was created in February 1627, when Morikawa Shigetoshi, a hatamoto in the service of Shōgun Tokugawa Hidetada acquired holdings in Sagami, Kazusa and Shimōsa Provinces with revenues exceeding the 10,000 koku necessary to qualify as a daimyō. He was allowed to build a jin'ya on the site of the Sengoku period Oyumi Castle. He later rose to the post of rōjū, and committed junshi on the death of Tokugawa Hidetada. His successors continued to rule Oyumi Domain until the Meiji Restoration.
As with most domains in the han system, Oyumi Domain consisted of several discontinuous territories calculated to provide the assigned kokudaka, based on periodic cadastral surveys and projected agricultural yields.[1] [2] The domain was centered on what is now Chuo Ward and Midori Ward of the city of Chiba.
| Name | Tenure | Courtesy title | Court Rank | revenues | |
| 1 | 1627–1632 | Dewa-no-kami (出羽守) | Lower 5th (従五位下) | 10, 000 koku | |
| 2 | 1632–1663 | Iga-no-kami (伊賀守) | Lower 5th (従五位下) | 10,000 koku | |
| 3 | 1663–1692 | Dewa-no-kami (出羽守) | Lower 5th (従五位下) | 10,000 koku | |
| 4 | 1692–1732 | Dewa-no-kami (出羽守) | Lower 5th (従五位下) | 10,000 koku | |
| 5 | 1732–1734 | Naizen-no-kami (内膳正) | Lower 5th (従五位下) | 10,000 koku | |
| 6 | 1734–1764 | Naizen-no-kami (内膳正) | Lower 5th (従五位下) | 10,000 koku | |
| 7 | 1764–1788 | Kii-no-kami (紀伊守) | Lower 5th (従五位下) | 10, 000 koku | |
| 8 | 1788–1838 | Naizen-no-kami (内膳正) | Lower 5th (従五位下) | 10,000 koku | |
| 9 | 1838–1855 | Dewa-no-kami (出羽守) | Lower 5th (従五位下) | 10,000 koku | |
| 10 | 1855–1858 | Dewa-no-kami (出羽守) | Lower 5th (従五位下) | 10,000 koku | |
| 11 | 1858–1862 | Dewa-no-kami (出羽守) | Lower 5th (従五位下) | 10,000 koku | |
| 12 | 1862–1871 | Naizen-no-kami (内膳正) | Lower 5th (従五位下) | 10,000 koku | |