Nii-jima (新島) is a volcanic Japanese island administered by the Tokyo Metropolitan Government. It is one of the Izu Seven Islands group of the seven northern islands of the Izu archipelago, and is located approximately 163 kilometres (101 mi) south of Tōkyō and 36 kilometres (22 mi) south of Shimoda Shizuoka Prefecture. The island is the larger inhabited component of the village of Niijima Village, Ōshima Subprefecture of Tokyo Metropolis, which also contains the neighboring island of Shikine-jima and the smaller, uninhabited Jinai-tō. Nii-jima is also within the boundaries of the Fuji-Hakone-Izu National Park.

The Izu Islands are a group of volcanic islands stretching south and east from the Izu Peninsula of Honshū, Japan. Administratively, they form two towns and six villages; all part of Tokyo Prefecture. The largest is Izu Ōshima, usually called simply Ōshima.