The Manly Dam is a heritage-listed dam near King Street, Manly Vale with a reservoir extending into Allambie Heights, both in the Northern Beaches Council local government area of New South Wales, Australia. It is often used as a place to have recreational activities. The reservoir is located within the Manly Dam Reserve. The dam was designed by the NSW Department of Public Works and built in 1892 by the Department. The reservoir and dam is owned by Sydney Water, an agency of the Government of New South Wales. The reservoir and dam was added to the New South Wales State Heritage Register on 18 November 1999.