Our present-day conception of an orc or ork is one of a race of mythical humanoid creatures, generally described as brutish, aggressive and repulsive, stemming from the writings of J. R. R. Tolkien, where orcs contrast with the benevolent Elvish race. The orcs are a race similar to the goblins. Tolkien developed his idea of the orc from the Old English term orcneas.

In popular culture, orcs are variously portrayed. Facial features tend toward the grotesque (generally a mixture of the ape-like and pig-like), and their skin typically a shade of green gray black, brown, or sometimes red. They may be physically stronger or weaker than humans, but almost always starkly different. They often ride boars, wolves, and wargs, and other unusual beasts.

In Tolkien's writings, Orcs are of human shape, of varying size but always smaller than Men. They are depicted as ugly and filthy, with a taste for human flesh. They are fanged, bow-legged and long-armed and some have dark skin as if burned. In a private letter, Tolkien describes them as "squat, broad, flat-nosed, sallow-skinned, with wide mouths and slant eyes... ...degraded and repulsive versions of the (to Europeans) least lovely Mongol-types". They are portrayed as miserable, crafty and vicious beings.

They fight ferociously as long as a guiding 'will' compels or directs them. Tolkien sometimes describes Orcs as mainly being battle fodder. Orcs are used as soldiers by both the greater and lesser villains of The Lord of the Rings, such as Sauron and Saruman.

Orcs eat all manner of flesh, including the flesh of Men. From descriptions and events relating to the Orcs, it seems likely that they indulge in cannibalism: in Chapter II of The Two Towers, Grishnákh, an Orc from Mordor, claims that the Isengard Orcs eat Orc-flesh, but whether that is true, or a canard spoken in malice, is uncertain. What does seem certain is that the Isengard Orcs resented that description. In that chapter Pippin is flung stale bread and an explicitly vague "strip of raw dried flesh... the flesh of he dared not guess what creature" by an Orc after a fight occurred in which the Uruk-hai killed several Orcs (though the dead flesh of the latter could not have been given to Pippin as it would not have had time to become dried but might well have been man-flesh if not that of some wild beast).