The Sagami Dam is a multi-purpose dam on the main stream Sagami River in Sagamihara, Kanagawa Prefecture on the island of Honshū, Japan.
The potential of the Sagami River valley for hydroelectric power development began to be developed in the 1930s, with the growth of population in the Shonan region, and the expansion of industry and electrical consumption in the Yokohama-Kanagawa industrial belt. Plans for a dam on the Sagami River were submitted to the Home Ministry in 1935, but approval was delayed in favor of other projects. Instead, the Kanagawa Prefectural Assembly passed the necessary regulations and secured a special budget to begin work in 1938. After actual construction work did not begin immediately, due to the strong opposition of the 196 families who needed to be relocated from the area to be flooded by the dam. However, the wartime demands for power and industrial water by the Yokosuka Naval Arsenal and by the Keihin Industrial complex became critical