Tanashi (田無市, Tanashi-shi) was a city located in the western portion of Tokyo Metropolis, Japan.

Because of the area's elevation relative to the Tamagawa River, traditional irrigation and rice farming was impossible.

After the Meiji Restoration it came under the jurisdiction of the short-lived prefectures of Shinagawa (1868) and Irima (1871), before becoming part of Kanagawa in 1872.

During the early Meiji period (1878) cadastral reform, it became the town of Tanashi within Kitatama District in Kanagawa.

The entire district was transferred to the administrative control of Tokyo Metropolis in 1893.