Château de Kankishiro, Medieval fortress in Hyōgo Prefecture, Japan.

Kanki Castle (Kanki-jō) was a flatland castle in Inami District, Harima Province, today part of Kakogawa, Hyōgo Prefecture. Its whole fortified area covered the village of Kanki and had four enclosures: Naka-no-maru, Higashi-no-maru, Nishi-no-maru and Ni-no-maru. A low tenshu is said to have stood in Naka-no-maru. Today Naka-no-maru is the site of Hōshōzan Jōraku-ji and Nishi-no-maru of Shinshū-ji; earthen ramparts and dry moats survive in part.

The Akamatsu clan built Kanki Castle, and Akamatsu Noritsugu of the Kanbe line took the Kanki estate in Innami District and founded it; his son Motoyori became lord and took the name Kanki. In 1578, during the Miki campaign, lord Kanki Yorisada sided with the Bessho against Hashiba Hideyoshi. About 2,000 defenders held out until the castle fell on 16 July 1578, after Yorisada's uncle Sadamitsu was turned and Yorisada assassinated.

The castle's name survives in two aliases, Manai-jō and Nakoshi-jō, and the whole Kanki settlement once formed its grounds, divided into four baileys: Naka-no-maru, Higashi-no-maru, Nishi-no-maru and Ni-no-maru. Naka-no-maru is now the site of Hōshō-zan Jōraku-ji, whose cemetery behind the main hall holds the grave of the castellan Kanki Sadayasu; Nishi-no-maru became Shinshū-ji. The site is listed as No. 48 of the 60 selections of My Town Kakogawa.

The castle site is now occupied by two temples: the central bailey (Naka-no-maru) is Hōshōzan Jōraku-ji and the western bailey (Nishi-no-maru) is Shinshū-ji. The grave of lord Kanki Sadayoshi lies in the cemetery behind Jōraku-ji's main hall. Remains of earthen ramparts and dry moats survive in places.

The castle's name is also written 奈幸子城, and the whole village of Kanki lay within its grounds, with four enclosures: Naka-no-maru, Higashi-no-maru, Nishi-no-maru and Ni-no-maru. Naka-no-maru is now the site of Hōshōzan Jōraku-ji, whose cemetery behind the main hall holds the grave of lord Kanki Sadayoshi. Earthworks and dry moats survive.