Self-harm is when someone hurts themselves on purpose, regardless of the reasons for doing this. Often, shame and stigma stop people from seeking help. Self-harming behaviour increases the risk of death by suicide, and it is a common cause of disability in young people. Currently, people attending health services only represent the tip of the iceberg; the proportion of teenagers self-harming has increased over the past 20 years—this is particularly so for young women and girls. The Lancet Commission on self-harm concludes that our cultures and societies play a major role in driving self-harming behaviours. The public health impact of self-harm has been neglected by governments globally. By delivering transformative shifts in societal attitudes, and initiating radical redesign of mental health care, we can fundamentally improve the lives of people who self-harm. Governments need to act to tackle the societal and commercial determinants of self-harming behaviours. The punishment of people who self-harm must stop. People who self-harm need better access to high-quality, compassionate services for support and treatment. Mainstream and social media outlets need to share information about self-harm responsibly and sympathetically.