Nirayama Castle (韮山城, Nirayama-jō) is a hilltop castle, now largely ruins, built by Hōjō Sōun in the Izu Province in 1493.

[4] The castle was well fortified, with western style fortifications, and had supporting forts on four nearby hills.

Garrisoned with 3600 men, it withstood a siege against it by 40,000 troops under the command of Oda Nobukatsu for 3 months, with the defenders only giving up when the main castle for the clan was lost.

[5] After the surrender, Tokugawa Ieyasu's retainer Naito Nobunari moved into the castle, respectively holding 10,000 koku to its name.

[6] The castle is now only ruins with some earthen walls and water moats.