Cambridge Reservoir is one of the four reservoirs owned by the City of Cambridge, Massachusetts, for its water supply. It is located in Waltham, near the border with Weston. It was created in 1910 by damming Hobbs Brook, a tributary of Stony Brook. The reservoir receives water from the Hobbs Brook Reservoir and the Stony Brook Reservoir, which are both upstream of it. The water from the Cambridge Reservoir is then conveyed to the Fresh Pond Reservoir in Cambridge, where it is treated and distributed to the city's customers.