Lake Sagami, Reservoir in Midori-ku, Japan.

Lake Sagami is a reservoir in Midori-ku in the Kanagawa region, created by damming the Sagami River. The body of water sits between forested slopes and serves as a drinking water source for nearby metropolitan areas.

The dam was completed in 1947 after World War II to supply water to the rapidly growing cities of Yokohama and Kawasaki. The project resulted in the relocation of several village communities that lived along the former river course.

The lake's name was chosen by Iwayatarō Uchiyama, a former governor of Kanagawa, and it was the first artificial lake in Japan to be named "—ko". The lakeside area has place names such as Katsura River, Arashiyama, Yose and Takao, said to derive from Kyoto: legend holds that Kōbō Daishi named them when he passed through, finding the terrain and peaks closely resembled the old capital's.

The pleasure boats and rental boats are concentrated on the northeastern shore by Sagami Lake Park, about 500 metres from JR Sagami Lake Station. Rental operators do not hire out boats or run sightseeing cruises during strong winds or between sunset and sunrise. The prefectural park has a paid car park that is free on weekdays.

No private boats are allowed on the lake: when the dam displaced local fishermen in 1947, families were given rental boats instead, and that arrangement still shapes who operates on the water. The rental operators also once kept old arcade games, including table-cabinet Space Invaders machines, at the lakeside.