This chapter describes the development of feminist theory regarding men and masculinities by synthesizing the strengths of three literatures: postmodern feminist debates on fluidity and difference in gender identity, feminist critiques of masculinism in international relations (IR), and the rapidly expanding literature on masculinities. It considers the politics of masculinity as a contested field of power moves and resistances rather than as a fixed set of power relations, and explores the relationships among different masculinities without losing sight of men’s overall position of power and privilege over women. The emphasis on power politics, then, reinforces the associations between such masculinities and power itself, associations that are crucial to masculinism. The nineteenth-century pathologizing of African masculinities has echoes in contemporary changes to hegemonic masculinity in the United States. If the boundaries of international politics inscribe it as a virtually all-male sphere, it follows that the content and qualities of IR will inform the definition and production of masculinities.