The Waterhen River is an east-flowing river in northwest Saskatchewan in the basin of the Beaver River (Canada). It is north of and parallel to the east-flowing part of the Beaver River and joins the north-flowing part of that river. It is at the southern edge of the boreal forest belt. The large Primrose Lake discharges south through the Martineau River into Cold Lake on the Alberta-Saskatchewan border. Cold Lake discharges east into the Cold River through Pierce Lake then into Lac des Iles. The Waterhen River begins on the east side of Lac des Iles and flows east to Waterhen Lake. Most of the river from Lac des Iles to Waterhen Lake is in Meadow Lake Provincial Park. East of Waterhen Lake the river leaves the park and flows east and somewhat north into the north-flowing part of the Beave