Yamanaka Castle was a Sengoku period yamajiro-style Japanese castle, built by the Odawara Hōjō clan in Tagata District, Izu Province, in what is now eastern Mishima, Shizuoka Prefecture, Japan. The ruins have been protected by the central government as a National Historic Site since 1988.

Mishima is a city located in eastern Shizuoka Prefecture, Japan. As of 31 July 2019, the city had an estimated population of 109,803 in 49,323 households, and a population density of 1,800 persons per square kilometre. The total area of the city is 62.02 square kilometres (23.95 sq mi).