Yokosuka Castle, Japanese castle in Kakegawa, Japan

Yokosuka Castle is a flatland castle in Kakegawa, Shizuoka Prefecture, built with stone walls of rounded boulders carried from the Tenryū River. Its keep was a four-story, three-roof structure. Today the site is a park with remains of moats, earthen ramparts and stone walls, and a local history museum stands within the former main bailey.

Yokosuka Castle was built in 1580 by Tokugawa Ieyasu's retainer Ōsuga Yasutaka as part of a ring of forts blockading Takatenjin Castle, which fell in 1581. The castle then became a regional administrative center. After the Tokugawa shogunate was established, it was expanded with water moats linked to the sea and stone-faced ramparts. The Nishio clan held it from 1682 until the Meiji Restoration in 1868.

The castle's name comes from the Edo-period Yokosuka Domain, which was ruled by the Nishio clan from 1682 until 1868. The domain's administrative center was here, and the Nishio family, including Nishio Tadanari who served as a rōjū, shaped the site's later history. Visitors can see the gate from the Ni-no-maru Bailey at Senyō-ji and a portion of the daimyō's palace at Yusan-ji.

The grounds now function as a public park where visitors can walk along preserved stone walls, moats, and earthen fortifications through marked pathways. Some areas feature uneven terrain, so wear suitable footwear for exploring the site.

Several original architectural elements survive today, including roof ornaments and demon tiles now preserved at Onkoji Temple and within sections of the palace at Yusan Temple. These pieces reveal the craftsmanship from the castle's earliest days.