Despite its importance, the phenomenon of dehumanization has been neglected by philosophers. Since its introduction, the term “dehumanization” has come to be used in a variety of ways. In this paper, I use it to denote the psychological stance of conceiving of other human beings as subhuman creatures. I draw on an historical example – Morgan Godwyn's description of 17th century English colonists' dehumanization of African slaves and use this to identify three explanatory desiderata that any satisfactory theory of dehumanization (...) needs to address. I then summarize and criticize the theories of dehumanization developed by Jacques-Philippe Leyens and Nicholas Haslam, focusing on what I take to be their misappropriation of the theory of psychological essentialism, and show that both of these approaches suffer from major difficulties. I finish with an assessment of the degree to which Leyens' and Haslam's theories satisfy the three desiderata mentioned earlier, conclude that they fail to address them, and offer a brief sketch of a more satisfactory approach to understanding dehumanization. (shrink)