Recent polls indicate that atheists are among the least liked people in areas with religious majorities (i.e., in most of the world). The sociofunctional approach to prejudice, combined with a cultural evolutionary theory of religion's effects on cooperation, suggest that anti-atheist prejudice is particularly motivated by distrust. Consistent with this theoretical framework, a broad sample of American adults revealed that distrust characterized anti-atheist prejudice but not anti-gay prejudice (Study 1). In subsequent studies, distrust of atheists generalized even to participants from more liberal, secular populations. A description of a criminally untrustworthy individual was seen as comparably representative of atheists and rapists but not representative of Christians, Muslims, Jewish people, feminists, or homosexuals (Studies 2-4). In addition, results were consistent with the hypothesis that the relationship between belief in God and atheist distrust was fully mediated by the belief that people behave better if they feel that God is watching them (Study 4). In implicit measures, participants strongly associated atheists with distrust, and belief in God was more strongly associated with implicit distrust of atheists than with implicit dislike of atheists (Study 5). Finally, atheists were systematically socially excluded only in high-trust domains; belief in God, but not authoritarianism, predicted this discriminatory decision-making against atheists in high trust domains (Study 6). These 6 studies are the first to systematically explore the social psychological underpinnings of anti-atheist prejudice, and converge to indicate the centrality of distrust in this phenomenon.