The black-headed duck is a South American duck in subfamily Oxyurinae of family Anatidae. It is found in Argentina, Bolivia, Brazil, Chile, Paraguay, and Uruguay.

The Oxyurini are a tribe of the duck subfamily of birds, the Anatinae. It has been subject of considerable debate about its validity and circumscription. Some taxonomic authorities place the group in its own subfamily, the Oxyurinae. Most of its members have long, stiff tail feathers which are erected when the bird is at rest, and relatively large, swollen bills. Though their relationships are still enigmatic, they appear to be closer to swans and true geese than to the typical ducks. The highest diversity is found in the warmer parts of the Americas, but at least one species occurs in a major part of the world.