Hinoyama Castle, Mountain fortress in Kitahiroshima, Japan.

Hinoyama Castle is a mountain castle on the roughly 700-metre Fire Mountain in Kitahiroshima, Hiroshima Prefecture, built near the summit and expanded over three generations until the whole slope was fortified. Its honmaru sits at the centre of a ring of enclosures defended by stone walls, stone ramparts and dry moats. The ruins are now heavily overgrown, with only fragments of the walls and moats visible.

Kikkawa Motoharu took over the Kikkawa clan in 1550 and rebuilt the small fort on Mount Hino as his base, moving from Ogurayama Castle. His son Motonaga and grandson Hiroie continued expanding it until the whole mountain was fortified. Motoharu retired to a residence at the foot in 1582, and the castle was abandoned after Hiroie moved to Gassan Toda Castle in 1591.

The name Hinoyama comes from the hill the castle was built on, written with the characters for "sun" and "field". The Kikkawa family moved their seat here from Ogurayama Castle in 1550, and the castle stayed in use through three generations until 1591. Volunteers now maintain the trail markers and mow the baileys under the banner "Revive Hinoyama Castle Ruins".

The ruins lie on a 700-metre hill, about 330 metres above the valley, and are reached on foot; the site is a 15-minute drive from the Ōasa interchange of the Hamada Expressway. Much of the mountain is overgrown, so paths are faint and stone walls and dry moats are best approached with care. Volunteers have set up signposts on the climbing route and mow the enclosures.

Archaeological excavations conducted between 1994 and 1998 uncovered building foundations, wells, and everyday objects from the fortress inhabitants. These discoveries reveal concrete details about how people lived and worked within this mountain stronghold.