Young women aged 15–24 years are at particularly high risk of HIV infection, accounting for 20% of new HIV infections among adults globally in 2015, despite accounting for just 11% of the adult population. In sub-Saharan Africa, young women accounted for 25% of new HIV infections among adults and women accounted for 56% of new HIV infections among adults. Gender inequalities, including gender-based violence, exacerbate women’s and girls’ physiological vulnerability to HIV and block their access to HIV services. Young people are denied the information and the freedom to make free and informed decisions about their sexual health, with most lacking the knowledge required to protect themselves from HIV. The impact of these barriers is strongest in high-prevalence settings, predominantly in eastern and southern Africa.