This paper examines how women in the North of Ireland used menstrual blood as a means of resisting the state. It explores the central role that menstrual blood and menstruation have played throughout the conflict – both as an instrument of war and as a weapon of resistance for female political prisoners. Various arms of the state used menstruation as a means of control over republican women. But women also used menstrual blood to challenge and to resist such attempts by the state. This article suggests that the use of menstrual blood in resisting the state is an act so subversive that it effectively disrupted staunchly entrenched gender norms in Northern Irish society prior to the height of the conflict. This in turn provoked the rise of a distinct form of feminism rooted within the republican movement.