Dehumanisation describes perceiving a person as nonhuman in some ways, such as lacking a mind. Social psychology is beginning to understand cognitive and affective causes and mechanisms—the psychological how and why of dehumanisation. Social neuroscience research also can inform these questions. After background on social neural networks and on past dehumanisation research, the article contrasts (a) research on fully humanised person perception, reviewing studies on affective and cognitive factors, specifically mentalising (considering another's mind), with (b) dehumanised perception, proposing neural systems potentially involved. Finally, the conclusion suggests limitations of social neuroscience, future research directions, and real-world consequences of this all-too-human phenomenon.