<p>Human dominance over other animals — expressed through exploitation, consumption and exclusion from moral concern — is a widespread feature of societies. However, this dominance contrasts with deep emotional bonds towards certain animals, especially companion animals, revealing a moral hierarchy in which human-assigned categories and functional roles shape how animals are valued and treated. In this Review, we synthesize psychological research on speciesism — the belief system that places humans above other animals and morally ranks animals according to their species and the roles humans impose upon them. We outline how people think about and evaluate different animals, how cognitive biases sustain moral disengagement, and how meat and animal-product consumption exemplify these dynamics in everyday life. We then review the ideological foundations that support speciesist beliefs and consider how speciesism intersects with other forms of prejudice shaped by dominance-based ideologies. Finally, we outline promising directions for future research, policy and psychological practice. Ultimately, recognizing speciesism as a powerful and pervasive belief system is essential for understanding human moral cognition and for building more ethical, sustainable and just relations with other animals.</p>