Kozukue Castle, Japanese hilltop castle in Kohoku-ku, Japan

Kozukue Castle is a hilltop castle ruin in Kozukue, Kohoku-ku, Yokohama, with two main enclosures and a narrow enclosure between them. Its defences were earthen: banks and dug ditches, with no stone walls. The western enclosure, labelled "honmaru", was partly cut by the Daisan Keihin Road, and the Yokohama Line's Shiroyama Tunnel runs beneath the western ridge. The hilltop is now wooded and the earthworks are hard to pick out from below.

Kozukue Castle was probably built by the Uesugi clan around 1438, during the Eikyo War, though the exact year is unknown. It first appears in records in 1478, when Ota Dokan attacked it during the Nagao Kageharu rebellion and took it after about two months. Restored around 1524 under Hojo Ujitsuna, it was abandoned after the 1590 Odawara campaign.

The name Kozukue comes from the village and district (Kozukue-go, Tachibana District, Musashi Province) where the castle stood. The Kasahara castellans invited monks and founded Unshō-in, the Sōtō temple in Kozukue-chō, and the Kasahara family graves there were registered as a Yokohama city historic site in 1994.

A 15-minute walk from Kozukue Station through the forest leads to the ruin, where the path can be uneven and slippery after rain. Sturdy footwear helps when exploring the slopes and ditches that run along the old defensive lines.

The site entered the Continued Top 100 Japanese Castles list in 2017, even though it never had stone walls. This recognition underlines the military value of earthen construction, which relied entirely on landform and ditches.