The coscoroba swan (Coscoroba coscoroba) is a species of waterfowl endemic to southern South America. It is the smallest of the birds called "swans", but still a large species of waterfowl. It belongs to the subfamily Anserinae in the family of ducks, swans, and geese, Anatidae. It is placed in the monotypic genus Coscoroba. The coscoroba swan is traditionally considered as an early branch from the common ancestor leading to true geese and swans, and recently genetic studies have associated a phylogenetic relationship between this species and Cape Barren goose (Cereopsis novaehollandiae) as sister groups.