A mill dam (International English) or milldam (US) is a dam constructed on a waterway to create a mill pond.

Water passing through a dam's spillway is used to turn a water wheel and provide energy to the many varieties of watermill. By raising the water level so that the overflow has farther to fall, a milldam increases the potential energy that a mill can harness and use for various tasks.^{[citation needed]}

Listed are here are some of the many examples of historic milldams and millponds (or place names taken from them).