Izunokuni is a city located in Shizuoka Prefecture, Japan. As of 10 July 2019, the city had an estimated population of 48,579 in 21,257 households and a population density of 506 persons per km2. The total area of the city is 94.62 square kilometres (36.53 sq mi).

The Izuhakone Railway Sunzu Line is a commuter railway line of the Izuhakone Railway, a private railroad in Japan. The line connects Mishima Station in the city of Mishima with Shuzenji Station in the city of Izu, both within Shizuoka Prefecture. The name "Sunzu" comes from the former provinces of Suruga and Izu, although the line at present operates only within the borders of former Izu Province.