A goose is a bird of any of several waterfowl species in the family Anatidae. This group comprises the genera Anser and Branta. Some members of the Tadorninae subfamily are commonly called geese, but are not considered "True Geese" taxonomically. More distantly related members of the family Anatidae are swans, most of which are larger than true geese, and ducks, which are smaller.

Anser is a waterfowl genus that includes the grey geese and the white geese. It belongs to the true goose and swan subfamily of Anserinae under the family of Anatidae. The genus has a Holarctic distribution, with at least one species breeding in any open, wet habitats in the subarctic and cool temperate regions of the Northern Hemisphere in summer. Some also breed farther south, reaching into warm temperate regions. They mostly migrate south in winter, typically to regions in the temperate zone between the January 0 °C (32 °F) and 5 °C (41 °F) isotherms.