Château de Yokochishiro, Medieval fortress in Japan.

Yokochishiro castle, also called Kinju-jo, is a ruined medieval mountain castle in Higashi-Yokochi, Kikugawa, Shizuoka Prefecture. It occupies ridges and valleys stretching from the Makinohara plateau toward the Kikugawa plain, measuring about 400 m east-west by 450 m north-south. Three main enclosures, Higashi-no-shiro, Naka-no-shiro and Nishi-no-shiro, sit along the ridge, with earthworks, moats and vertical trenches still visible.

The Yokochi clan, local lords recorded in the Azuma Kagami, built the castle in the early Muromachi period, though some date it to the mid-15th century. In 1476, during a conflict between Imagawa Yoshitada and Shiba Yoshikane, the Yokochi sided with the Shiba and were attacked; the castle burned and fell, and lord Yokochi Hidekuni was killed. Imagawa Yoshitada was himself killed on the return march at Shiokaisaka in Totomi.

The Yokochi clan, who built the castle, are said to be the ancestors of the Yokochi surname across Japan. The castle's other name, Kinjujo, is remembered locally, and the nearby valley called "Kintama otoshi no tani" is known as an unusual place name. The site is now part of the Kikugawa Castle Sites, a national historic site since 2004.

The ruins lie on a hill ridge on the Makinohara plateau above the Kikugawa river plain, with three main sections, Higashi-no-shiro, Naka-no-shiro and Nishi-no-shiro, linked along the ridge. Earthworks, moats and vertical-cut trenches remain, so wear walking shoes. Excavations continue and the whole area belongs to the Omaezaki Enshunada Prefectural Natural Park.

The Yokochi clan, who built the castle, are said to be the ancestors of the Yokochi surname across Japan. Nearby is a valley called "Kintama Otoshi no Tani", known as an unusual place name. The castle site was designated a national historic site on 30 September 2004 as part of the Kikugawa Castle Sites group.