Château de Kaifu, Japanese castle in Tokushima Prefecture, Japan

Kaifu Castle, also called Tomo Castle, is a ruined castle in Kaiyō, Tokushima Prefecture, on the site of a fortification built by the Kaifu clan in the Eiroku era (1558–1570). No keep or wooden buildings remain; the site is a designated town historic site, and the nearby inlet where the castle's harbour once lay is still visible.

Kaifu Castle, also called Tomo Castle, was built in the Eiroku era (1558–1570) by Kaifu Tomomitsu. In 1571 his men attacked a boat sheltering in the inlet below the castle and killed Shima Chikamasu, brother of Chōsokabe Motochichi. Motochichi took the castle in 1577. Under the Hachisuka it became one of the nine castles of Awa, abolished in 1638 by the one-castle-per-province decree.

The castle is also called Tomo-jō. After its 1638 abandonment under the one-castle-per-province law, a district office of Kaifu County operated on the site until 1807, when it moved to present-day Minami. The site is now a historic site designated by Kaiyō town.

Kaifu Castle is a ruin: no keep or restored buildings stand, only earthworks and stone outlines in the hills above Kaiyō. The site is a designated town historic site, so stay on the paths and leave the earthworks undisturbed. Bring water and sun protection; the walk up is unshaded in places.

The castle is also called Tomo-jō, and its site is a designated historic site of Kaiyō. After the castle was abandoned in 1638, a district office of Kaifu County stood here until it was moved to present-day Minami in 1807.