The Étang Grenon (French for "Grenon Pond" or "Grenon Lake") is a significant freshwater wetland located on Oléron Island, off the west coast of France. Situated within the Charente-Maritime department in the Nouvelle-Aquitaine region, it lies near the commune of Saint-Pierre-d'Oléron.
The étang is recognized as an important ecological site, characterized by its diverse flora and fauna. It serves as a vital stopover and breeding ground for various migratory bird species, making it a popular location for birdwatching and nature observation. The surrounding area is typically flat and marshy, contributing to its rich biodiversity, which includes a range of aquatic plants, insects, and other wildlife. Its conservation is part of broader efforts to protect the natural heritage and unique wetland ecosystems of Oléron Island and the Atlantic coastline.