Lake Mary Ann (Warumungu: Tingkkarli) and previously known as Mary Ann Dam up until 7 December 2005, is an earth- and rockfill embankment dam across the Mary Ann Creek, located approximately north of Tennant Creek, in the Northern Territory of Australia. Situated just off the Stuart Highway and completed in 1980, the resultant reservoir was built exclusively for recreational purposes. Some water sports, such as swimming or canoeing, can be conducted surrounded by landscaped grassy areas on one side and natural bushland on the other.
The Waramungu people have lived in the area of Tingkkarli for thousands of years. After colonisation, it was pegged as mining lease GML441E by Nugget Wilson and Bill Howes and Harold Williams. Wilson and Howes named the mine 'Mary Ann' after their respective daughters Mary Jean and Wendy Ann. The nearby watercourse then became known as Mary Ann Creek or Mary Ann Billabong.
Originally the site was investigated with a view to increase the water supply for Tennant Creek and Peko Mine in the late 1940s, and later again in the mid-1950s. In 1977, local residents proposed that a recreational dam could be constructed close to Tennant Creek. The Northern Territory Government supported the proposal and construction commenced during 1979 and 1980.
The dam wall was completed in April 1980, was filled for the first time in January 1981, and was officially opened on 24 April 1981 by the Hon Ian Tuxworth, named as the Mary Ann Dam. In December 2005, the reservoir was renamed as Lake Mary Ann.
The earth and rock-filled dam wall is high and long and contains of rockfill. The impounded reservoir, when full, holds a maximum of and covers , drawn from a catchment area of . The uncontrolled spillway has capacity of .
In 2014, a Federal Court determined seven native title claims in the area of Lake Mary Ann covering .