PURPOSE: Adolescent girls and young women (AGYW) in South Africa experience a disproportionately high burden of HIV acquisition. National HIV prevalence among AGYW increases nearly three-fold during the transition from late teenage years to their early twenties. We investigated whether beliefs about gender equity influence subsequent HIV acquisition among AGYW in South Africa. METHODS: We used data from the HIV Prevention Trials Network 068, a longitudinal conditional cash transfer study of AGYW in Mpumalanga Province, South Africa. Gender-equitable beliefs were measured at the level of the individual and summarized among school peers and adults in the community using the Gender Equitable Men's Scale (GEMS). Generalized estimating equation regression was used to assess the association between individual, peer and community GEMS and HIV incidence, herpes simplex virus type 2 (HSV-2) incidence, and other HIV risk factors while accounting for repeated observations and clustering. RESULTS: A total of 2,533 AGYW were followed up for up to 5 years. Adjusting for potential confounders, a unit increase in peer GEMS scores (i.e. more equitable) were significantly protective against subsequent HIV acquisition (risk difference = -.019; 95% confidence interval: -.032, -.006) and subsequent HSV-2 acquisition (risk difference = -.020; 95% confidence interval: -.040, -.000). Low individual and community GEMS scores were associated with multiple HIV risk factors but not with HIV or HSV-2 incidence directly. CONCLUSION: School-level peer endorsement of gender equity may be protective against HIV and HSV-2 incidence among AGYW. Interventions that increase gender equity at the individual level and at the level of the social environment, particularly among school peers, have the potential for protective effects on the health of AGYW.