This entry first looks at the history of utilitarianism, from thinkers like Bentham to modern ideas like Singer’s work and the Effective Altruism movement. It defines utilitarianism by its core features: consequentialism, welfarism, and sum-ranking (often with maximization), and discusses their implications, such as its egalitarian nature and demandingness. Then, it discusses how utilitarianism and psychology connect, focusing on two main things. First, it looks at why people often do not make utilitarian judgments. This is often because of their intuitions or emotions. Second, it discusses what kind of people tend to make utilitarian choices. This includes looking at dual-process theories and the difference between instrumental harm and impartial beneficence. The chapter also looks critically at current research, especially about animal welfare. It argues that the important idea of hedonistic welfarism in utilitarianism is often overlooked. Lastly, it talks about future ideas, like how to help people make more utilitarian judgments and why empathy is important.