Iino Jin'ya, Government office in Futtsu, Japan

Iino Jin'ya was the administrative headquarters of Iino Domain in present-day Futtsu, Chiba Prefecture. Its buildings are gone; what remains is a large compound of about 176,000 m² divided into an inner enclosure with honmaru, ninomaru and sannomaru, and a western outer enclosure. A 5–6 m wide, 1.2–2 m deep outer moat and earthen ramparts about 2 m high still surround the inner enclosure.

The building was founded in 1648 by Hoshina Masasada and served as a regional administrative center under the Tokugawa shogunate. It played an important role in managing and controlling local territories across several generations.

The name Iino comes from the territory granted to Hoshina Masasada in Kazusa Province. Within the ni-no-maru stood the Iino Shrine, enclosed by earthen walls on three sides, and a gunpowder store built on the site of the Inarizuka burial mound. In the late Edo period the domain school, Meishinkan, was built into the eastern slope of the Sanjozuka kofun.

The site lies on the alluvial plain of the lower Koito River in Futtsu, Chiba Prefecture, at about 7 to 8 metres elevation. No buildings survive; the earthworks and moats are best seen in the inner compound, whose outer moat is a prefectural historic site. The moat is 5 to 6 metres wide and 1.2 to 2 metres deep, with a bank about 2 metres high. Excavations have been carried out since 1981 as housing was built, so parts of the former grounds are now residential.

The jin'ya was built inside the Kunaizuka kofun cluster: the keyhole-shaped Sanjōzuka kofun, 122 m long, served as a lookout and its outer moat became the moat of the western compound. The han school Meishinkan was later built by cutting into its eastern mound.