The defence of diminished responsibility was introduced in the Homicide Act 1957. As a defence to murder, when used successfully it reduced to manslaughter the conviction for those charged with murder and who were suffering from an abnormality of the mind. The Coroners and Justice Act 2009 significantly reformed the defence following concerns being raised about the clarity of terminology used in the defence, and the fairness of its use. The reformed defence is now one of two partial defences to murder, sitting alongside that of loss of control. This chapter will explore the use of the diminished responsibility defence in the context of women who kill their abusers. It will begin by providing a brief overview of the evolution of the defence, before moving on to critically consider the consequences and limitations of its use in cases of women who kill their abusers. In particular, it will focus on how the defence has pathologized the actions of women who kill their abusers, reinforcing damaging gender stereotypes around women’s mental instability, and ultimately denying women’s agency. Finally, the chapter will contemplate the future of the diminished responsibility defence in the context of the potentially emerging role of coercive control in supporting defences for women who kill their abusive partners.