The Mary River flows in the Northern Territory of Australia and is a site of the Mary River National Park.
The river is approximately 225 kilometres long and rises about 50 kilometres east of Pine Creek. The catchment area is over 8,000 square kilometres but is ephemeral and only flows in the wet season, during the dry it is a series of pools and billabongs.
The catchment has several small reserve areas forming the Mary River National Park to help protect it. The Arnhem Highway crosses the river near one of the park areas. It also supports multiple land uses including pastoralism, fishing, mining, defence force, tourism, conservation, and horticulture. Pastoralism, particularly cattle grazing is the dominant use, taking up 63% of the catchment area.
The river has a total of ten tributaries, including the Little Mary River, MacKinlay River, Bowerbird Creek, Mingloo Creek and Douglas Creek. It has a mean annual outflow of 2,400 gigalitres
