INTRODUCTION: Stigma and disclosure concerns have been key barriers to oral pre-exposure prophylaxis (PrEP) adherence for African adolescent girls and young women (AGYW) in efficacy trials. We aimed to understand the impact of these factors among African AGYW in an open-label PrEP study. METHODS: HPTN 082 was an open-label PrEP study among AGYW (ages 16 to 24) in Harare, Zimbabwe, and Cape Town and Johannesburg, South Africa from 2016 to 2018. Women starting PrEP were randomized to standard adherence support (counselling, two-way SMS, monthly adherence clubs) or standard support plus drug-level feedback. Serial in-depth interviews were conducted among 67 AGYW after 13-week and 26-week study visits to explore experiences of stigma, disclosure and PrEP adherence. We analysed data by coding transcripts and memo-writing and diagramming to summarize themes. RESULTS: AGYW described stigma related to sexual activity (e.g. "people say I'm a prostitute") and being perceived to be living with HIV because of taking antiretrovirals (e.g. "my husband's friends say I'm HIV infected"). Participants who anticipated stigma were reluctant to disclose PrEP use and reported adherence challenges. Disclosure also resulted in stigmatizing experiences. Across all sites, negative descriptions of stigma and disclosure challenges were more common in the first interview. In the second interview, participants often described disclosure as an "empowering" way to combat community-level PrEP stigma; many said that they proactively discussed PrEP in their communities (e.g. became a "community PrEP ambassador"), which improved their ability to take PrEP and encourage others to use PrEP. These empowering disclosure experiences were facilitated by ongoing HPTN 082 study activities (e.g. counselling sessions, adherence clubs) in which they could discuss PrEP-related stigma, disclosure and PrEP adherence issues. CONCLUSIONS: Stigma and disclosure challenges were initial concerns for African AGYW newly initiating PrEP but many were empowered to disclose PrEP use over their first six months of PrEP use, which helped them cope with stigma and feel more able to take PrEP regularly. PrEP programmes can foster disclosure through community and clinic-based discussion, adherence clubs and activities normalizing sexual behaviour and PrEP use, which can reduce stigma and improve PrEP adherence and thus effectiveness.