Psychological essentialism suggests that categories are stable, fixed at birth, and based on biological factors. The present paper examined some factors that encourage gender essentialism among US college students. In two studies (Study 1: 53 female, 22 male; Study 2: 55 female, 48 male), participants completed questionnaires assessing essentialist beliefs regarding a range of gendered concepts. They also completed several questionnaire measures of gender stereotyping and gender beliefs. Results revealed: (1) greater essentialism among men than women; (2) greater essentialism of masculine (vs. feminine) concepts, and; (3) for men, greater essentialism among those who report greater conformity to masculine norms. These data suggest that masculinity is more narrowly defined than femininity, not only in stereotyped beliefs but also in essentializing.