| Rivière au Rat | |
| Subdivision Type1: | Country |
| Subdivision Name1: | Canada |
| Subdivision Type2: | Province |
| Subdivision Name2: | Quebec |
| Subdivision Type3: | Region |
| Subdivision Name3: | Estrie |
| Subdivision Type4: | Municipality |
| Subdivision Name4: | Weedon |
| Length: | 8.5km (05.3miles) |
| Source1: | Mountain streams |
| Source1 Location: | Weedon |
| Source1 Coordinates: | 45.7211°N -71.3836°W |
| Source1 Elevation: | 268m (879feet) |
| Mouth: | Saint-François River |
| Mouth Location: | Weedon |
| Mouth Coordinates: | 45.705°N -71.435°W |
| Mouth Elevation: | 232m (761feet) |
| Progression: | Saint-François River, Saint Lawrence River |
| Tributaries Left: | (upstream) 5 streams |
| Tributaries Right: | (upstream) 1 stream |
The Rat River is a tributary of the Saint-François River. The "Rat River" flows in the municipality of Weedon, in the Le Haut-Saint-François Regional County Municipality, in the region administrative Estrie, Quebec, Canada.
The hydrographic slopes adjacent to the "Rat River" are:
The "Rat River" has its source in a forest environment on the boundary of the former municipalities of Weedon and Fontainebleau, on the west side of the mine road, west of Lake Elgin and east of Lake Louise.
Its course of first heads south-west in parallel (south-east side) to Saint-François River, then turns north-west along the path of Fontainebleau, to its mouth. Its course passes at north of the village center of Fontainebleau.
The "Rat River" flows onto the south bank of the Saint-François River, upstream from the Fontainebleau road bridge and downstream of the mouth of Lake Louise.
The toponym "Rivière au Rat" was formalized on December 5, 1968, at the Commission de toponymie du Québec.[1]