Sagamihara is a city in Kanagawa Prefecture, Japan. As of 1 May 2021, the city has an estimated population of 723,470, with 334,812 households, and a population density of 1,220 persons per km2. The total area of the city is 328.91 square kilometres (126.99 sq mi). Sagamihara is the third-most-populous city in the prefecture, after Yokohama and Kawasaki, and the fifth most populous suburb of the Greater Tokyo Area. Its northern neighbor is Machida, with which a cross-prefectural merger has been proposed.

Kanagawa Prefecture is a prefecture of Japan located in the Kantō region of Honshu. Kanagawa Prefecture is the second-most populous prefecture of Japan at 9,221,129 and third-densest at 3,800 inhabitants per square kilometre (9,800/sq mi). Its geographic area of 2,415 km2 (932 sq mi) makes it fifth-smallest. Kanagawa Prefecture borders Tokyo to the north, Yamanashi Prefecture to the northwest and Shizuoka Prefecture to the west.