The Secretary Bird or Secretarybird (Sagittarius serpentarius) is a very large, mostly terrestrial bird of prey. Endemic to Africa, it is usually found in the open grasslands and savannah of the sub-Saharan region. Although a member of the order Accipitriformes, which also includes many other diurnal raptors such as kites, buzzards, vultures, and harriers, it is given its own family, Sagittariidae.

First described by English illustrator John Frederick Miller in 1779, the secretarybird was soon assigned to its own genus, Sagittarius, by French naturalist Johann Hermann in his Tabula Affinatum Animalium. It was not until 1935 that the species was moved to its own family, distinct from all other birds of prey—a classification confirmed by molecular systematics.

Its common name is popularly thought to derive from the crest of long quill-like feathers, lending the bird the appearance of a secretary with quill pens tucked behind their ear, as was once common practice. A more recent hypothesis is that "secretary" is borrowed from a French corruption of the Arabic saqr-et-tair or "hunter-bird."

The generic name "Sagittarius" is Latin for "archer," perhaps likening the secretarybird's "quills" to a quiver of arrows, and the specific epithet "serpentarius" recalls the bird's skill as a hunter of reptiles.[8] Alternatively, the name could refer to the last two constellations in the Zodiac, Sagittarius and Serpentarius (now known as Ophiuchus).[citation needed]

The secretarybird has distinct black feathers protruding from behind its head
The secretarybird is instantly recognizable as having an eagle-like body on crane-like legs which increases the bird’s height to as much as 4 ft tall. This bird has an eagle-like head with a hooked bill, but has rounded wings. Body weight can range from 5.1 to 10.1 lb and height is 35–54 in. Total length from 44 to 60 in and the wingspan is 75–87 in. The neck is not especially long, and can only be lowered down to the inter-tarsal joint, so birds reaching down to the ground or drinking must stoop to do so.

Secretarybirds prefer open grasslands and savannas rather than forests and dense shrubbery which may impede their cursorial existence. While the birds roost on the local Acacia trees at night, they spend much of the day on the ground, returning to roosting sites just before dark.

Secretarybirds often use kicks to incapacitate and kill their prey, with the bird's sharp claws piercing the victim's body. Their kicks are incredibly powerful; they are capable of shattering a human's hand with a single kick.