3 Dam and Gatehouse is a historic waterworks facility in Framingham, Massachusetts, United States.

They were built 1876–78 as part of an expansion of the public water supply of the city of Boston.

The dam is 2,280 feet (690 m) long, and impounds an area of 253 acres (102 ha) in the Sudbury River watershed.

At the end of the overfall area nearest Route 9 stands the gatehouse, a granite structure with a rectangular main block and a smaller wing.

It houses controls for two 4-foot (1.2 m) mains connected to the Sudbury Aqueduct via the gatehouse at Reservoir No.