The Antler River is located in the Prairie Pothole Region of North America's Great Plains in south-eastern Saskatchewan and south-western Manitoba in Canada in an area known as Palliser's Triangle. Its source is in Saskatchewan's Moose Mountain Upland and it is a major tributary of the Souris River. As a result, its flood levels are monitored by the United States Geological Survey. The Antler River Recreation District is an association of communities in the south-western corner of Manitoba that are on or near the river and its related branches. Towns involved include Melita and Pierson.