The Masked Duck (Nomonyx dominicus) is a small stiff-tailed duck ranging through the tropical Americas. They are found from Mexico to South America and also in the Caribbean. Primarily non-migratory, Masked Ducks are reported as very uncommon vagrants in the southernmost United States, along the Mexican border and in Florida.

The only member of the genus Nomonyx, it is intermediate between the rather primitive Black-headed Duck (Heteronetta) and the very apomorphic true stifftails. It is sometimes included with the latter in the genus Oxyura, but apparently the Masked Ducks of our time are the descendants of a missing link in the Oxyurinae evolution, having changed but little for millions of years..

Breeding adult males have a rust-colored body with a black face and mottled wings. Adult females, winter males and juveniles have a barred brownish gray body, with 2 horizontal darkly colored stripes running through the buffy colored face.

These ducks mainly feed on seeds,roots and leaves of aquatic plants. They also eat aquatic insects and crustaceans. They feed by diving. Masked Ducks breed in any freshwater water body with dense marsh vegetation and surrounded by heavy tree cover. They also occur in mangrove swamps. These ducks are usually very secretive, but they are not rare and not considered threatened by the IUCN.