The aim of this thesis is to analyse the triangular dynamics of securitisation and desecuritisation underpinning the European Union’s policies against trafficking in women for sexual exploitation. Drawing on two main bodies of literature: critical security studies and feminist insights into prostitution and trafficking, it sheds light on the growing tendency of the European Union to conceptualise and address trafficking in women for sexual exploitation as a security issue, and on the distinct and competing approaches that coexist within feminist struggles against such trend, which largely follow the opposing views that structure feminist debates on prostitution: an abolitionist stance that is articulated predominantly from inside the European Union’s institutions and a sex-work approach that is defended mainly from outside. The fundamental contribution this thesis makes is to show that the European Union’s securitising tendency and the abolitionist ideals defended therein are not antithetical but inextricably linked. By means of a Critical Frame Analysis of the Union’s internal security, gender and sexuality and anti-trafficking policies, I show that the evolution of trafficking in women for sexual exploitation as a security issue within the Union’s Area of Freedom, Security and Justice, and its evolution as a form of violence against women in its gender equality and sexual diversity policies are inextricably linked, and that this link is central to its securitisation. I start from the premise that trafficking in women is securitised by ‘contagion’, that is, by being conceptualised and addressed as an epiphenomenon of organised crime, irregular migration and prostitution. The key mechanism enabling this ‘contagion’ in the European Union is spillover of the internal market into a project of internal security; a spillover that is itself the result of a process of securitisation in which terrorism, organised crime and irregular migration are linked and depicted as threats to the internal security of the Union. The inclusion of human trafficking as a form of organised crime and irregular immigration in such a continuum is, therefore, what allows trafficking in women for sexual exploitation to be securitised as a result.