The horned guan (Oreophasis derbianus) is an endangered species in an ancient group of birds of the family Cracidae, which are related to the Australasian megapodes or mound builders (Megapodiidae).

Given that the basal relationships of the living cracids are not well resolved, the horned guan is often placed in its own subfamily Oreophasinae.

The sexes are alike in plumage but males have a taller horn and longer wings, tail, and legs than females.

[1] The horned guan feeds mostly on a very wide variety of fruits; green leaves are a significant part of its diet with flowers and possibly insects eaten in small amounts.

[6][7][9][10] Most of the information about the horned guan's breeding biology comes from Mexico in a study published in 1995.

Its nest is an oval structure of dry leaves and roots place high in a tree and usually near running water.

[6][10] The IUCN originally in 1988 assessed the horned guan as Threatened, then in 1994 as Vulnerable, and since 2000 as Endangered.

Its range has contracted due to logging, firewood gathering, conversion of forest to agriculture, and subsistence hunting pressure.

Climate change is further expected to exacerbate horned guan population declines by inducing shifts in the species' already restricted range".