The Dartmouth Dam is a large gravity dam across the Mitta Mitta, Gibbo and Dart rivers, the Morass Creek and a number of small tributaries. The dam is located near Mount Bogong in the north-east of the Australian state of Victoria. The dam's purpose includes irrigation, the generation of hydroelectricity, water supply and conservation. The impounded reservoir is called Dartmouth Reservoir, sometimes called Lake Dartmouth. The Dartmouth Power Station, a conventional hydroelectric power station generates power to the national grid, is located near the dam wall. The dam is Australia's tallest dam, at 180 metres (590 ft).

A smaller pond, called the Dartmouth Dam Regulating Pond or Banimboola Pondage, approximately 9 kilometres (6 mi) downstream of the main dam, also across the Mitta Mitta River, is located adjacent the Banimboola Hydroelectric Power Station and forms part of the Dartmouth Dam complex of facilities.

Developed by the State Rivers & Water Supply Commission of Victoria, construction of the dam commenced in 1973, engineered by the Snowy Mountains Engineering Corporation, and was completed in 1979 by Thiess Brothers, at a cost of A$179 million. The cost was shared equally by the Commonwealth, Victorian, New South Wales and South Australian governments.

The dam wall rises to a height of 180 metres (591 ft) from the lowest part of the foundation to the roadway across the top of the dam, making the dam wall the highest in Australia. The core component materials of the wall include 10.5 million m³ (370 million cu ft) of rock, 0.8 million m³ (28 million cu ft) of filter material made from crushed quarried rock, and 2.8 million m³ (99 million cu ft) of earth for the core. When full, the reservoir has a capacity of 3,856 gigalitres (3,126,000 acre⋅ft), or approximately 6.7 times the capacity of Sydney Harbour; and can release a maximum outflow of approximately 12 GL (3.2 billion US gal) per day in normal operation.

The crest of the uncontrolled chute spillway is 486 metres (1,594 ft) AHD and is approximately 92 metres (302 ft) long. When full, flood flows spill over the crest and down an 80-metre-long (260 ft) concrete chute. The water then returns to the river via an open rock stepped cascade which gradually widens to 300 metres (984 ft) at river level. Once the Dartmouth Reservoir reaches 99% capacity, it is considered to be 'operationally full'. Releases are then set to pass inflows downstream to prevent the level rising further.

Releases are passed through the outlet works and power station whenever possible. Water will only flow over the spillway if significant flood inflows enter from upstream when the storage is close to full. This approach reduces the chance of downstream flooding, maximises operating flexibility for hydro-power generation, and protects the spillway. Since the dam's construction, major spill events have occurred only five times and, as of November 2024^[update], the most recent were in Spring in 1996 and 2022.

In 2005 Engineers Australia awarded the dam as a National Engineering Landmark under their engineering heritage recognition program.

The Dartmouth Reservoir stores water from the Victorian High Country's snow fields for summer release into the Mitta Mitta, and the downstream Lake Hume, and into the greater Murray River for irrigation. The reservoir's inflow and outflow capacity is quite small considering its size, meaning that its levels vary little compared with some other dams on the Murray and their tributaries.