| Native Name: | 飯田藩 |
| Conventional Long Name: | Iida Domain |
| Common Name: | Iida Domain |
| Subdivision: | Han |
| Status Text: | under Tokugawa shogunate Japan |
| Government Type: | Daimyō |
| Today: | Nagano Prefecture |
| Year Start: | 1601 |
| Year End: | 1871 |
| Era: | Edo period |
thumb|right|site of the donjon of Iida Castle, administrative centre of Iida Domain was a feudal domain under the Tokugawa shogunate of Edo period Japan. It is located in Shinano Province, Honshū. The domain was centered at Iida Castle, located in what is now part of the town of Iida in Nagano Prefecture.[1] It was also known as .
The area around Iida had been ruled during the Sengoku period by Akiyama Nobutomo, a retainer of Takeda Shingen. After the destruction of the Takeda clan, the lands came under the control of Tokugawa Ieyasu and were ruled by Suganuma Sadatoshi, followed by Mori Hideyori, and Kyōgoku Takatomo. Following the Battle of Sekigahara and the establishment of the Tokugawa shogunate, Ogasawara Hidemasa was relocated to Iida from Koga Domain in Shimōsa Province and made daimyō with Iida Domain, a 50,000 koku holding in Shinano Province. After his transfer to Matsumoto Domain in 1613, the territory reverted to tenryō status ruled directly by the shogunate until 1617, when it was reassigned to Wakizaka Yasumoto, formerly of Ōzu Domain in Iyo Province. His son, Wakizaka Yasumoto followed, reducing the domain by 2,000 koku with a gift to one of his uncles. He was transferred to Tatsuno Domain in Harima Province in 1672, where his descendants resided to the Meiji restoration.
The Wakizawa were replaced by a junior branch of the Hori clan and the holdings of the domain were reduced to 20,000 koku. The domain's finances were never in good condition, and the situation continued to deteriorate over the years leading to widespread rioting in 1762 and in 1809. The 10th daimyō, Hori Chikashige was a close supporter of Mizuno Tadakuni and held important posts within the Shogunal government, including rōjū. the domain as increased to 27,000 koku, but was dropped to 17,000 koku on the failure of the Tenpō Reforms and subsequent backlash. During the Bakumatsu period, the domain lost another 2,000 koku for failing to stop passage of anti-government forces through its territory during the Mito rebellion.
During the Boshin War, the domain supported the imperial side. In July 1871, with the abolition of the han system, Iida Domain briefly became Iida Prefecture, and was later merged into the newly created Nagano Prefecture. Under the new Meiji government, Hori Chikahiro, the last daimyō of Iida Domain was given the kazoku peerage title of shishaku (viscount).
As with most domains in the han system, Iida Domain consisted of several discontinuous territories calculated to provide the assigned kokudaka, based on periodic cadastral surveys and projected agricultural yields.[2] [3]
| Name | Tenure | Courtesy title | Court Rank | kokudaka | Notes | ||
| Ogasawara clan (fudai) 1601-1613 | |||||||
| 1 | 1600-1613 | Hyobu-daifu (兵部大輔) | Lower 5th (従五位下) | 50,000 koku | transfer from Koga Domain | ||
| tenryō 1613-1617 | |||||||
| Wakizaka clan (tozama / fudai) 1617-1672 | |||||||
| 1 | 1617-1654 | Awaji-no-kami (淡路守) | Lower 5th (従五位下) | 55,000 koku | transfer from Ōzu Domain | ||
| 2 | 1654-1672 | Nakatsukasa-no-sho (中務少輔) | Lower 5th (従五位下) | 55,000 -> 53,000 koku | |||
| Hori clan (tozama / fudai) 1672-1871 | |||||||
| 1 | 1672-1673 | Mimasaka-no-kami (美作守) | Lower 5th (従五位下) | 20,000 koku | transfer from Karasuyama Domain | ||
| 2 | 1673-1685 | Suo-no-kami (周防守) | Lower 5th (従五位下) | 20,000 koku | |||
| 3 | 1686-1697 | Suo-no-kami (周防守) | Lower 5th (従五位下) | 20,000 koku | |||
| 4 | 1697-1715 | Yamato-no-kami (大和守) | Lower 5th (従五位下) | 20,000 koku | |||
| 5 | 1715-1728 | Wakasa-no-kami (若狭守) | Lower 5th (従五位下) | 20,000 koku | |||
| 6 | 1728-1746 | Yamato-no-kami (大和守) | Lower 5th (従五位下) | 20,000 koku | |||
| 7 | 1746-1779 | Yamato-no-kami (大和守) | Lower 5th (従五位下) | 20,000 koku | |||
| 8 | 1779-1784 | Yamashiro-no-kami (山城守) | Lower 5th (従五位下) | 20,000 koku | |||
| 9 | 1784-1796 | Yamato-no-kami (大和守) | Lower 5th (従五位下) | 20,000 koku | |||
| 10 | 1796-1846 | Yamato-no-kami (大和守) | Lower 4th (従四位下) | 20,000 ->27,000 -> 17,000 koku | |||
| 11 | 1846-1868 | Iwami-no-kami (石見守); Jijū (侍従) | Lower 5th (従五位下) | 17,000 ->15,000 koku | |||
| 11 | 1868-1871 | Mimasaka-no-kami (美濃守) | Lower 5th (従五位下) | 15,000 koku | |||