This chapter aims to broaden the conversation of international relations to include its simultaneous reliance on and refusal to theorize hegemonic masculinities. It reviews the feminist perspectives on topics at the heart of international relations (IR) conduct and inquiry. Many perspectives frame theoretical debates in IR: realism, neorealism, critiques of these mainstream IR theories, and feminism. Contemporary feminisms analyze not only patterns of difference constituted by the dichotomies of maleness and femaleness but also patterns of differences among women. The radical feminist insight that the personal is political transgresses the definitive political boundary: the one that divides public from private and excludes the latter from what counts as politics. Feminists argue that the dichotomy of masculine-feminine is a structural feature of the social life, rendering gender an analytical category with systemic implications for advancing our understanding of social relations.