This article develops loneliness as a political and social justice issue by illustrating the harmful personal and social consequences of the medical jurisdiction over and constitution of variations in sex characteristics. Whilst connections between loneliness, health and illness have been well established, this work customarily identifies the ways illness can lead to, or be caused by, loneliness. Instead, I provide an account of the central role of medicalisation and medical management in producing loneliness. By doing so, I underline the imperative (...) for medical practice to consider its influence upon social and personal, as well as physical, wellbeing. Drawing on stories shared through solicited diaries followed by in-depth interviews with seven people with sex variations and two parents in the UK, I show how accounts of loneliness help to illuminate the violence of abandonment, silencing and marginalisation that often goes unheard, together with hidden or normalised systems of harm. Building on concepts of ethical loneliness and ontological loneliness, I show how structural violations operate to injure trust and self-worth, leading to social unease. I argue for the importance of people with sex variations finding sites of comfort and acceptance, but note the ways that some forms of medicalisation can inhibit alliances and community formation, despite diagnoses also carrying the potential to facilitate informal support structures and collective identities. By bringing together intersex studies with discourses of loneliness, I develop a better understanding of loneliness as a product of social and systemic violence, and the ways in which medical discourses tie in with larger structures of oppression, coercion and control. This article concludes by underlining the need for structural change in our approach to and understanding of sex variations, and with a call for us to become more attentive to these stories of medical harm, to ensure that they are heard and to seek necessary justice. (shrink)