Understanding and remedying women’s underrepresentation in majority-male fields and occupations require the recognition of a lesser-known form of cultural bias called masculine defaults. Masculine defaults exist when aspects of a culture value, reward, or regard as standard, normal, neutral, or necessary characteristics or behaviors associated with the male gender role. Although feminist theorists have previously described and analyzed masculine defaults (e.g., Bem, 1984; de Beauvoir, 1953; Gilligan, 1982; Warren, 1977), here we define masculine defaults in more detail, distinguish them from more well-researched forms of bias, and describe how they contribute to women’s underrepresentation. We additionally discuss how to counteract masculine defaults and possible challenges to addressing them. Efforts to increase women’s participation in majority-male departments and companies would benefit from identifying and counteracting masculine defaults on multiple levels of organizational culture (i.e., ideas, institutional policies, interactions, individuals).