Young women in southern Africa experience some of the highest incidence rates of HIV infection in the world. Across southern Africa, HIV prevalence among women increases rapidly between the teenage years and young adulthood. Adult HIV prevalence is 16.8 % in South Africa, 23 % in Botswana, 23 % in Lesotho, and 26.5 % in Swaziland. Existing research has illuminated some of the key social, behavioral, and structural factors associated with young women's disproportionate HIV risk, including gendered social norms that advantage male power in sexual relationships and age disparities in relationships between younger women and older male partners. Important structural factors include the region's history of labor migration and legacy of family disruption, and entrenched social and economic inequalities. New interventions are emerging to address these high levels of HIV risk in the key population of young women, including structural interventions, biomedical prevention such as PrEP, and combined HIV prevention approaches.