Abstract Women are usually represented as victims in the literature on conflict and conflict resolution. While women are indeed victims of violence in the context of conflict, this representation excludes the experiences of women who have joined and fought in illegal armed groups. Little is known about the lives of women who fight alongside men in illegal militarized organizations. These women are often overlooked during peace negotiations and in the design and implementation of Disarmament, Demobilization, and Reintegration programs, affecting their conditions and experiences during the transition to civilian life. The Colombian conflict presents an important case study regarding the militarization of women in illegal armed groups, and the experience of demobilization, and is the focus of this dissertation. To address this case study, the concept of “militarized gender performativity” is advanced, drawing on the works of Cynthia Enloe and Judith Butler. In the Colombian case, both left–wing and right–wing armed groups have incorporated women into their ranks. This research elucidates the effects of non–state militarism on the social processes that produce and reproduce gender systems in two of Colombia's illegal armed groups, uncovering how the FARC and the AUC construct, negotiate, challenge, or reinforce gender roles. The research indicates that there are significant differences in the way this is done. Interviews with ex–combatants from the FARC and the AUC show that women's sexuality plays a central role in the militarization of women combatants in both organizations, but there are specific policies that establish the nature of the relationships in each group. These differences represent distinct militarized femininities which maintain aspects of traditional gender relations while transforming others according to the needs of the organization in question. The transformation of gender identities in each of the armed groups reveals the performative nature of gender roles in a militarized context.