The Rivière du Loup is a river in eastern Quebec, Canada, which empties on the south shore of Saint Lawrence River at the city of Rivière-du-Loup, which is part of the regional county municipality (RCM) Rivière-du-Loup, in the administrative region of Bas-Saint-Laurent.

There is a hydroelectric plant on the river near the city.

The Rivière du Loup (English: "river of the Wolf") has its source in Saint-Pierre Lake (Lac Saint-Pierre) in the geographic township of Painchaud in the Kamouraska Regional County Municipality, which is in the Notre Dame Mountains and the Zone d'exploitation contrôlée (English: Controlled Harvesting Zone) of Zec Chapais.^[1] This lake is located 36.5 km (23 miles) east of the southeast coast of the Gulf of St. Lawrence, 20 km (12 miles) southeast of the village center of Saint-Bruno-of-Kamouraska and 20 km (12 miles) south-west of the village center of Saint-Athanase.

The Rivière du Loup flows to the north over 101.3 kilometers (63 miles), coursing through the regional county municipalities of:

• MRC Kamouraska: municipalities (starting from the upstream)
  • Mont-Carmel
  • Saint-Bruno-de-Kamouraska
  • Sainte-Hélène-de-Kamouraska
  • Saint-Joseph-de-Kamouraska
  • Saint-Alexandre-de-Kamouraska
• MRC Rivière-du-Loup: municipalities (starting from the upstream)
  • Saint-Antonin
  • Notre-Dame-du-Portage
  • Rivière-du-Loup city.

At its mouth, the Rivière du Loup pours over a long ledge (at low tide) in the "Cayes to Carrier Bay" which is bordered on the north side by the Pointe-de-Rivière-du-Loup. From Malin Rock, this edge advances towards the southwest in the St. Lawrence River over a length of 1.6 km (1 mile), including the end where a marina is fitted.

The river's mouth is located in front of the Île aux Lièvres (English: Island of Hare) and the Île Blanche (English: White Island), located 10 km (6 miles) offshore and part of the municipality of Saint-André-de-Kamouraska. The Channel "Pot à l'Eau-de-Vie" (English: "Pot of stream water") separates the island and the southeast coast of St. Lawrence River. The Estuary Islands Wildlife Reserve (Réserve faunique des Îles de l'Estuaire) was built on a set of islands between the Île aux Lièvres and the channel Pot à l'Eau-de-Vie.

The river's name means Wolf River in French and may have come from a native tribe known as "Les Loups" or from the many seals, known in French as loup marin, once found at the river's mouth.^[1]