La Vallée-de-la-Rivière-Sainte-Marguerite Biodiversity Reserve, up to 2022 known as Réserve Aquatique de la Vallée-de-la-Rivière-Sainte-Marguerite, is a biodiversity reserve in Quebec (Canada), located in the Saguenay-Lac-Saint-Jean and Côte-Nord regions. This 321 km2 protected area is dedicated to conserving the ecosystems of the Sainte-Marguerite River valley. The latter is located in a glacial valley separating the Saguenay Graben from the Monts Valin. The proximity of these two physiographic units favors the diversity of the flora, with several species at the northern limit of their range.

A biodiversity reserve of Quebec is a protected area established to promote maintenance of biodiversity in the terrestrial environment and more specifically to maintain representatives of the various natural regions of Quebec, Canada. There are five biodiversity reserves in Quebec with permanent protection status.