Iida Castle, Japanese castle in Iida, Nagano Prefecture

Iida Castle was a hilltop castle built on the tip of a river terrace between the Matsukawa and Nosoko, tributaries of the Tenryu River. Its east side held the honmaru, enclosed by earthen walls and about 100 m square, with a palace and seven buildings; west of it lay the ninomaru, Sakuramaru and demaru enclosures toward the cliff.

It was built in the early 13th century by the Banzai clan and later passed between powerful lords such as Takeda Shingen and Tokugawa Ieyasu. These shifts in control reflected the changing politics of the region across several centuries.

The main bailey became the grounds of Nagahime Shrine, founded there in 1880, and stone ramparts, dry moats and earthen walls survive around it. The secondary bailey held Iida Nagahime High School from 1921 to 1982; since 1989 the Iida City Museum of Art and History stands on the site. At the Sakuramaru site, the gate of the former lord's residence survives beside the prefectural government office.

The site is within a 15-minute walk from JR Iida Station or accessible by the city's circular bus to the Prefectural Office stop. It is easy to visit as part of a day trip through the city.

The Sakuramaru Gate, completed in 1754, is the only castle building still standing on its original site. Its gatehouse with a separate roof projecting at the side is the only such example in Nagano Prefecture. The gate stayed closed for 14 years until it was opened in March 1999 for the viewing of the married couple cherry trees.