Every day, millions of women and girls worldwide experience violence. This abuse takes many forms, including intimate physical and sexual partner violence, female genital mutilation, child and forced marriage, sex trafficking, and rape. The Lancet Series on Violence against women and girls shows that such abuse is preventable. Five papers cover the evidence base for interventions, discuss the vital role of the health sector in care and prevention, show the need for men and women to be involved in effective programmes, provide practical lessons from experience in countries, and present a call for action with five key recommendations and indicators to track progress.