This chapter examines the relationship between gender and security, distinguishing between ‘practical’ and ‘discursive’ aspects of such relationship and exploring the problematizing of gendered roles through Queer Theory. Practical aspects are exemplified by the concrete role of women in militaries, or as victims, bystanders, or helpers of military conflict or of militarization in general. Discursive aspects are exemplified by the traditional connections made between militarism and masculinity and between nurturing, peace, and femininity. The chapter first explains what gender means and why issues of gender are relevant to understanding security. It shows how understanding and placing notions of gender at the centre of any debate on security can help us comprehend the way men and women relate to insecurity, violence, and war. Theorists have often discussed gender and security by referring to war and peace, but the chapter stresses the need to pay attention to the post-conflict environment.