Rivière des Marsouins – Grand Étang Important Bird Area

Rivière des Marsouins – Grand Étang Important Bird Area is an 1,800-hectare (6.9 sq mi) tract of land on the island of Réunion, a French territory in the western Indian Ocean.

The IBA lies on the north-eastern side of the island in the commune of Saint Benoît, extending over an altitude range of 83–1334 m above sea level.

It comprises the steep-sided valley of the Rivière des Marsouins and the lake of Grand Étang.

The 30 ha Grand Étang (“Big Pond” in English), the largest lake on the island, was formed in an adjoining valley which was blocked by lava flowing from the volcano of Piton de la Fournaise.

The site contains largely unmodified native plant communities, including evergreen lowland forest.