Negoya Castle, Japanese castle in Shōrakuji, Japan

Negoya Castle is an earthwork castle in Shōrakuji, Saitama Prefecture, on the north shore of Lake Sayama. It measures 150 m north-south and 75 m east-west, with a double moat and earthen ramparts enclosing the main and secondary enclosures; by the end of its use it had eight or nine enclosures. No stone walls or towers remain.

Negoya Castle was built between 1390 and 1428 by Yamaguchi Takatada, son of Yamaguchi Takaharu, on the north shore of what is now the Yamaguchi reservoir (Sayama Lake) in Shōrakuji, Tokorozawa. Originally called Ryūgaya or Shōrakuji Castle, it served as the wartime refuge of the Yamaguchi family, who lived in the settlement below and at Yamaguchi Castle in peacetime. After the Yamaguchi fell under Hōjō control, the castle was repeatedly repaired and held by retainers such as Fushimi Kotarō and Yamazumi Hikosaburō.

The name Negoya derives from a nearby settlement and means "sleeping hut"; the castle was also called Ryūdani or Shōrakuji Castle. In peacetime the Yamaguchi lords lived in the village or at Yamaguchi Castle and withdrew here only in wartime. A slope called Kotarō-zaka, named after its builder Takatada, once stood nearby but its site is now unknown.

The castle site lies on the north shore of the Yamaguchi reservoir (Sayama Lake) in Shōrakuji, Tokorozawa, within a Tokyo Metropolitan Government water-protection area fenced off by the Tokyo Metropolitan Waterworks Bureau. Entry is restricted and the castle ruins are not open to the public. Until the early 1970s only a simple fence stood here, and some visitors climbed over it to see the earthworks.

The castle sits on the north shore of Lake Sayama, a reservoir built in modern times; it narrowly escaped flooding during construction. Until the early 1970s only a simple fence stood around the site, and some visitors climbed over it to see the earthworks. Today the area is fenced off as a Tokyo Metropolitan water-resource protection zone.