Waterhen River is an east-flowing river in the north-west area of the Canadian province of Saskatchewan in the drainage basin of the Beaver River. It is north of and parallel to the east-flowing part of the Beaver River and joins the north-flowing part of that river. Most of the river and its drainage basin is at the southern edge of the boreal forest belt. While the river's source is Lac des Îles, its drainage basin reaches north into the Mostoos Hills and west well into the neighbouring province of Alberta.