Sugaya Yakata, Japanese castle ruins in Ranzan, Saitama Prefecture, Japan

Sugaya Yakata is a medieval castle site situated near the confluence of two rivers on the Kantō plain. The grounds feature multiple rectangular defensive zones defined by earthen ramparts of varying heights.

Tradition holds that Sugaya Yakata began as the fortified residence of Hatakeyama Shigetada (1164-1205), a leading retainer of Minamoto no Yoritomo, though no relics from that period have been excavated. In 1488, during the Chōkyō War, Ōta Sukeyasu rebuilt the old fort for the Yamanouchi Uesugi, and the defeated Ōgigayatsu Uesugi Akitaka was briefly confined there. It later passed to the Later Hōjō and was abandoned after 1590.

The name Sugaya comes from the place name, not a family: the site lies in Ōaza Sugaya, Ranzan. The Hatakeyama clan moved its fortified residence here from Hatakeyama-no-shō to control the Kamakura Kaidō. The Saitama Prefectural Ranzan Historical Museum now stands on the grounds, and the site was chosen as No. 120 of the Continued Top 100 Japanese Castles in 2017.

The site is accessible on foot in about 15 minutes from Musashi-Ranzan Station on the Tobu Tojo Line. A museum located on the grounds provides information about the history and structure of the fortification.

This represents a hirajiro design built on flat land, unlike typical mountaintop castles found across Japan. Proximity to the rivers provided water access and transportation connections, making it valuable for trade.