Background: As adolescent girls and young women (AGYW) transition to adulthood, their interaction with their social context becomes a critical consideration for HIV prevention interventions. Few studies have examined what types of community groups and community spaces might be protective for AGYW HIV acquisition and related sexual behaviors. Methods: Data were obtained from HIV Prevention Trials Network 068, a longitudinal study of AGYW (age 13–20 years) in rural South Africa. Survival analyses and generalized estimating equations were used to assess whether community group membership and time spent in community spaces were associated with HIV incidence and sexual behaviors (unprotected sex, transactional sex, and having an older partner). Results: A total of 2245 AGYW were followed up for up to 4 years. Membership in church groups [adjusted hazard ratio (aHR): 0.75, 95% confidence interval (CI): 0.53 to 0.91] and dance groups (aHR: 0.89, 95% CI: 0.80 to 0.98) and spending time at church (aHR: 0.88, 95% CI: 0.79 to 0.98) were protective for HIV infection. Conversely, spending time at taverns was associated with higher HIV incidence (aHR: 1.27, 95% CI: 1.15 to 1.41). Membership in church groups and spending time at a family member's home and at church were protective for all 3 sexual behaviors. Spending time at a boyfriend's home and taverns was risky for all 3 sexual behaviors. Conclusions: The results suggest that community spaces and community groups that include an element of adult supervision are potentially protective, whereas spaces and groups that provide an opportunity for AGYW to interact unsupervised with boyfriends or meet new partners are potentially risky.