Nyakuichiōji-jinja, Shinto shrine in Japan

Nyakuichiōji-jinja is a Shinto shrine in Ōmachi whose main hall, built in 1556 by Nishina Moriyasu, is a single-bay Kasuga-zukuri structure with cypress-bark roofing, designated an Important Cultural Property. Its grounds hold a Kannon Hall of 1706 with a thatched hip-and-gable roof and a single three-storied pagoda erected in 1711. A small earthen bank separates the shrine buildings from the Buddhist ones.

The shrine traces its origin to the reign of Emperor Suinin, when Nishina Ō, ruler of the area, enshrined the water deity Izanami. In the Kamakura period, Nishina Moritō, who had visited Kumano in Kii Province, invited the deity Nyakuichi Ōji from Nachi Taisha's fifth hall and made it protector of Nishina Manor. The main hall was built in 1556 by Nishina Moriyasu and is an Important Cultural Property.

The shrine keeps both Shinto and Buddhist buildings: a torii and main sanctuary stand beside a Kannon Hall and a three-storied pagoda. During the Meiji era's anti-Buddhist campaign, locals built small earthen banks between the buildings and argued that shrine and temple were separate, so both survived. The Kannon Hall enshrines an eleven-faced Kannon, held to be the original Buddhist counterpart of Nyakuichiōji.

The shrine is about a ten-minute walk from Kita-Ōmachi Station on the JR Ōito Line. The precinct covers 17,186.4 m² of cedar woodland, designated a Nagano Prefecture natural monument in 1965, so allow time to walk the paths between the main hall, Kannon Hall and pagoda. The yabusame rite falls on 17 July, with a thanksgiving ceremony on the fourth Sunday of July.

In July, the Nyakuichiōji Festival takes place here, where young boys dressed in historical costumes ride horses and shoot arrows at targets in traditional horseback archery called Yabusame. This festival is one of only a few events of its kind still held in Japan, bringing the community together to pass down old customs.