The ducks, geese and swans (Anatidae) comprises 168 species occurring on all the world's continents except Antarctica and on most of the world's islands and island groups. A few species have been domesticated for agriculture, and many others are hunted for food and recreation. Five species have become extinct since 1600, and many more are threatened with extinction.

The ducks, geese and swans are small to large sized birds that have a general body plan that is broad and elongated. Diving species vary from this in being rounder. Extant species range in size from the Cotton Pygmy Goose, at as little as 26.5 cm and 164 grams, to the Trumpeter Swan, at as much as 183 cm and 17.2 kg.

Anatids are generally herbivorous as adults, feeding on various water-plants, although some species also eat fish, molluscs, or aquatic arthropods. One group, the mergansers, are primarily piscivorous, and have a serrated bill to help them catch fish. In a number of species, the young include a high proportion of invertebrates in their diet, but become purely herbivorous as adults.