| Rivière du Castor | |
| Subdivision Type1: | Country |
| Subdivision Name1: | Canada |
| Subdivision Type2: | Province |
| Subdivision Name2: | Quebec |
| Subdivision Type3: | Region |
| Subdivision Name3: | Saguenay-Lac-Saint-Jean |
| Subdivision Type4: | MRC |
| Subdivision Name4: | Le Domaine-du-Roy |
| Subdivision Type5: | Municipality |
| Subdivision Name5: | Sainte-Hedwidge et Saint-Prime |
| Length: | 13km (08miles) |
| Source1: | Confluence of two forest streams |
| Source1 Location: | Sainte-Hedwidge |
| Source1 Coordinates: | 48.5386°N -72.4458°W |
| Source1 Elevation: | 416m (1,365feet) |
| Mouth: | Rivière à l'Ours |
| Mouth Location: | Saint-Prime |
| Mouth Coordinates: | 48.6231°N -72.4286°W |
| Mouth Elevation: | 101m (331feet) |
| Progression: | Ashuapmushuan River, Lac Saint-Jean, Saguenay River |
| River System: | Rivière à l'Ours, Ashuapmushuan River, Lac Saint-Jean, Saguenay River |
| Tributaries Left: | (upstream) Cayouette stream, Lachance stream, three unidentified streams. |
| Tributaries Right: | (upstream) Allard-Dorval stream. |
The rivière du Castor (English: River of the Beaver) is a tributary of Rivière à l'Ours, flowing successively in the municipalities of Sainte-Hedwidge and Saint-Prime, in the Le Domaine-du-Roy Regional County Municipality, in the administrative region of Saguenay–Lac-Saint-Jean, in the province of Quebec, in Canada.
The Beaver River valley is served by the 3rd range road, the Marcel-Auclair road and the 6th range road.[1]
Forestry and agriculture are the main economic activities in this valley.
The surface of the Beaver River is usually frozen from the beginning of December to the end of March, except the rapids areas; however, safe traffic on the ice is generally from mid-December to mid-March.
The Beaver River originates at the confluence of two forest streams (altitude:), in Sainte-Hedwidge. This source is located at:
From its source, the Beaver river flows over with a drop of especially in forest areas, according to the following segments:
The Beaver river flows into a bend on the south bank of the Rivière à l'Ours, on the southwest side of the 3rd range road. This confluence is located at:
From the mouth of the Beaver river, the current successively descends the course of the Rivière à l'Ours on toward the North-east; the Ashuapmushuan River towards the south-east on ; then crosses lake Saint-Jean east on (ie its full length), follows the course of the Saguenay River via the Petite Décharge on east to Tadoussac where it merges with the Saint Lawrence Estuary.[2]