Psychological essentialism is an ordinary mode of category representation that has powerful social-psychological consequences. This article reviews those consequences, with a focus on the distinctive ways people perceive, evaluate, and interact with members of human categories they essentialize. Why and when people engage in this mode of thinking remain open questions. Variability in essentialism across cultures, categories, and contexts suggests that this mode of representing human categories is rooted in a naturalistic theory of category origins, combined with a need to explain differences that cross category boundaries.