Gujō Hachiman Castle, Japanese castle on Mount Hachiman in Gujō, Japan.

Gujō Hachiman Castle is a yamajiro on Hachiman Hill above the Yoshida River in Gujō, Gifu Prefecture. Its 1933 reconstructed keep is a four-storey wooden tower modelled on Ōgaki Castle, with white plaster walls, small rectangular windows under projecting tiled gables, and stacked roofs with upturned eaves. It stands on a dark stone foundation wall, with two corner turrets and a plaster wall.

Endō Morikazu built a fort on Ushikubi Mountain (later Hachiman Mountain) in 1559, destroying the Tō clan based at Akataniyama Castle. In 1588 Inaba Sadamichi rebuilt the castle with a moat, a tenshudai, raised ramparts and an expanded ninomaru. After the Battle of Sekigahara, Endō Keitaka returned as lord; the castle was demolished in 1870, leaving only stone walls, and the present four-storey wooden tower was built in 1933 modelled on Ōgaki Castle.

The castle's name comes from Hachiman, the district of Gujō where it stands. A shrine inside the grounds honours Oyoshi, a 17-year-old girl said to have been buried as a human pillar when repairs stalled; during the Gujō Odori dance season a fair called Oyoshi Matsuri is held in Shimodono-machi below. The castle also issues a gold Goshuin stamp on the last Friday of each month.

The castle stands on Hachiman Mountain above the Yoshida River, and the entrance can be reached on foot or by car, with parking at the foot of the hill. Near that parking area are statues of Yamauchi Kazutoyo and his wife Chiyo. The castle grounds are a Gifu Prefecture-designated historic site, and the reconstructed keep houses a history museum.

The 1933 tower is a rare wooden mock keep, and the oldest surviving wooden castle reconstruction in Japan. Inside, look for the "power stone": a 350 kg boulder that the legendary Akahige Sakubei is said to have carried up alone during earlier construction work.