The Orks, also called Greenskins, are a savage, warlike, green-skinned species of bestial, asexual humanoids who are spread all across the galaxy. They are unique among the intelligent xenos species known to Mankind in that they possess the physiological features of both animals and fungi. They share many physical and cultural features with the dark fantasy Warhammer universe's Orcs (and were initially called "Space Orcs" to distinguish them).

Orks are seen by their enemies (pretty much everyone else in the universe) as primitive, barbaric, hyper-violent, and crude, but they are the most successful and widepsread intelligent species in the whole galaxy, outnumbering possibly every other intelligent starfaring species, even Humanity (with the very plausible exception of the Tyranids).