The king vulture (Sarcoramphus papa) is a large bird found in Central and South America. It is a member of the New World vulture family Cathartidae. This vulture lives predominantly in tropical lowland forests stretching from southern Mexico to northern Argentina. It is the only surviving member of the genus Sarcoramphus, although fossil members are known.

Large and predominantly white, the king vulture has gray to black ruff, flight, and tail feathers. The head and neck are bald, with the skin color varying, including yellow, orange, blue, purple, and red. The king vulture has a noticeable orange fleshy caruncle on its beak. This vulture is a scavenger and it often makes the initial cut into a fresh carcass. It also displaces smaller New World vulture species from a carcass. King vultures have been known to live for up to 30 years in captivity.

King vultures were popular figures in the Mayan codices as well as in local folklore and medicine. Although currently listed as Least Concern by the IUCN, they are decreasing in number, due primarily to habitat loss.

The king vulture was originally described by Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae as Vultur papa, the type specimen originally collected in Suriname. It was reassigned to the genus Sarcoramphus in 1805 by French zoologist André Marie Constant Duméril. The generic name is a Neo-Latin compound formed from the Greek words σάρξ (sarx, "flesh", the combining form of which is σαρκο-) and ῥάμφος (rhamphos, "crooked beak of bird of prey"). The genus name is often misspelled as Sarcorhamphus, improperly retaining the Greek rough breathing despite agglutination with the previous word-element. The bird was also assigned to the genus Gyparchus by Constantin Wilhelm Lambert Gloger in 1841, but this classification is not used in modern literature since Sarcoramphus has priority as the earlier name. The species name is derived from the Latin word papa "bishop", alluding to the bird's plumage resembling the clothing of one. The king vulture's closest living relative is the Andean condor, Vultur gryphus. Some authors have even put these species in a separate subfamily from the other New World vultures, though most authors consider this subdivision unnecessary.

There are two theories on how the king vulture earned the "king" part of its common name. The first is that the name is a reference to its habit of displacing smaller vultures from a carcass and eating its fill while they wait. An alternative theory reports that the name is derived from Mayan legends, in which the bird was a king who served as a messenger between humans and the gods. This bird was also known as the "white crow" by the Spanish in Paraguay. It was called cozcacuauhtli in Nahuatl, derived from cozcatl "collar" and cuauhtli "bird of prey".

The exact systematic placement of the king vulture and the remaining six species of New World vultures remains unclear. Though both are similar in appearance and have similar ecological roles, the New World and Old World vultures evolved from different ancestors in different parts of the world. Just how different the two are is currently under debate, with some earlier authorities suggesting that the New World vultures are more closely related to storks. More recent authorities maintain their overall position in the order Falconiformes along with the Old World vultures or place them in their own order, Cathartiformes. The South American Classification Committee has removed the New World vultures from Ciconiiformes and instead placed them in Incertae sedis, but notes that a move to Falconiformes or Cathartiformes is possible. Like other New World vultures, the king vulture has a diploid chromosome number of 80.

The genus Sarcoramphus, which today contains only the king vulture, had a wider distribution in the past. The Kern vulture (Sarcoramphus kernense), lived in southwestern North America during the mid-Pliocene (Piacenzian), some 3.5–2.5 million years ago). It was a little-known component of the Blancan/Delmontian faunal stages. The only material is a broken distal humerus fossil, found at Pozo Creek, Kern County, California. As per Loye H. Miller's original description, "[c]ompared with [S. papa] the type conforms in general form and curvature except for its greater size and robustness." The large span in time between the existence of the two species suggests that the Kern vulture might be distinct, but as the fossil is somewhat damaged and rather non-diagnostic, even assignment to this genus is not completely certain. During the Late Pleistocene, another species probably assignable to the genus, Sarcoramphus fisheri, occurred in Peru. A supposed king vulture relative from Quaternary cave deposits in Cuba turned out to be bones of the eagle-sized hawk Buteogallus borrasi (formerly in Titanohierax).

Little can be said of the evolutionary history of the genus, mainly because remains of other Neogene New World vultures are usually younger or even more fragmentary. The teratorns held sway over the ecological niche of the extant group, especially in North America. The Kern vulture seems to slightly precede the main bout of the Great American Interchange, and notably the living diversity of New World vultures seems to have originated in Central America. The Kern vulture would therefore represent a northwards divergence possibly sister to the S. fisheri – S. papa lineage. The fossil record, though scant, supports the theory that the ancestral king vultures and South American condors separated at least some 5 mya.