Abstract The proposed supplement is within scope of Specific Aims 1 and 2 in our parent ITEST study (UH3HD096929). The supplement focus on the same participant population (AYA in Nigeria), use the same conceptual framework (youth participatory action research), uses the same methodologies (crowdsourcing open calls), adopts the same focus on implementation science, and similarly will help to decrease HIV incidence among at-risk AYA. Our findings from initial AYA crowdsourcing activities in Nigeria suggested that AYA had limited understanding of PrEP. In 2020, there were few PrEP demonstration projects or national guidance that recommended the use of PrEP. As a result, our randomized controlled trial did not have PrEP uptake as a secondary outcome and did not focus on PrEP. However, there have been four major recent shifts that provide a unique opportunity to now focus on PrEP and inform Nigerian national PrEP use among AYA: (1) There are now more demonstration projects focused on PrEP among at- risk individuals, including adolescents (REFS); (2) the national Nigerian HIV prevention guidelines explicitly recommend the use of PrEP;4 (3) youth-led community engagement programs conducted by our UH3 project demonstrate that AYA are interested and willing to start PrEP (REFS); (4) excellent rates of linkage from HIV self-testing into youth-friendly clinics and STD testing from our UH3 study suggest that this could be a feasible mechanism to organize HIV prevention services for at-risk Nigerian AYA. The proposed supplement logically builds on the foundation from the 2021 crowdsourcing open call and 2022 designathon which both focused on ways to enhance PrEP uptake among AYA in Nigeria. We will draw on the strong resources, infrastructure, and relationships that have been developed in the initial phases of this study. The proposed supplement will be led by the Nigerian Institute of Medical Research and supported by St. Louis University and the University of North Carolina at Chapel Hill, the three key partners which led the parent UH3 study. Our skills, experience, and knowledge make our team uniquely qualified to organize this research.