Recent scholarship surrounding questions of masculinity demonstrates that masculinity is not a natural, homogeneous category but a social construction that varies across space and time. This ethnography explores what constitutes masculinity among the Nùng Fan Slìng (Nùng), a Tai-speaking ethnic minority living in Northeastern Vietnam, through an examination of cultural assumptions that premise social practices and relationships that construct and reproduce gendered identities. Data, generated by qualitative ethnographic research methods and interpreted through the interdependent analytic categories of culture, identity, and gender, reveal that Nùng masculinity cannot be characterized as dichotomously opposed to, nor as formed in isolation from femininity. Rather, masculinity is reproduced in a system of gendered relations structured around the patrilineage. The socialization of boys as permanent and girls as provisional members of patrilineages construct men as primal and women as marginal members of Nùng society. Nùng assumptions and practices, such as conceptions of love, flirting, and men’s and women’s sexuality reveal that male-female relationships are often marked by distance and contestation. Husband-wife relationships show that gendered practices and positions of married men and women are marked by practicality and masculine privilege. Men’s practices, positions, and relationships, including those of Nùng priests, illuminate Nùng masculinity as founded upon permanence and privilege within the patrilineage, rather than on characteristics exclusively associated with men. However, men’s patrilineal privilege is buttressed by assumptions that men have greater capacity than women for the same kinds of characteristics. Drawing on Nùng concepts of self and difference, Taoist conceptions of yin-yang, and animist beliefs I argue that the inequalities between men and women, in terms of human characteristics, are overlapping differences of degree. Drawing on local Confucianist prescripts for ordering hierarchical social relationships I argue that the disparities between men and women in terms of power and privilege are reproduced by gendered positions within the patrilineage. Cultural assumptions about the nature of men and women, and gendered practices, positions, and relationships demonstrate that heightened spiritual, mental, and physical capacity taken together with patrilineal permanence constitute the hegemonic form of masculinity among the Nùng.