若森県庁, Former prefectural government office site in Wakamori, Tsukuba, Japan

The Wakamori Prefecture Office was the administrative seat of Wakamori Prefecture, established in 1869 in what is now Wakamori, Tsukuba. Its compound covered 4 chō (about 39,668 m²) on a tongue-shaped plateau on the right bank of the Sakura River, with the main office, a jail and longhouses at Tate-no-yama and 13 longhouses at Mukaiyama. The site, about 25 m above sea level, is now a city historic site with earthen embankments on private land.

The site was a castle in the Nanboku-chō period, built by Oda Haruhisa, and later a hatamoto Honda family jinya that was demolished in 1863. In 1869 the prefecture office was built here after a campaign by village headman Ōkubo Yasuke; it opened on 1 April 1869 and was abolished in December 1871, its buildings split and sold in 1872.

The office's arrival drew people from some 560 villages, and inns called gōshuku, offering rest and mediation for petitioners, opened alongside chazuke-ya eateries. In September 1869 the ten inns and nineteen eateries signed an agreement dividing their roles after quarrels over customers. The place name Wakamori survives in Tsukuba, and the site is a city historic spot.

The site lies in Wakamori, Tsukuba, about ten minutes on foot from the Wakamori-minami bus stop. It is private land holding a private house and a chestnut orchard, so there is no entry; the earthworks can be seen from outside. Buildings moved elsewhere are also privately owned and closed to visitors.

The site is a Tsukuba City historic site, but the office buildings are gone: in 1872 the structure was split into four parts and handed to private owners and Jiyunuma Elementary School. One relocated farmhouse keeps a roof tile with a chrysanthemum crest; the buildings are private and cannot be visited.