In Malaysia, there is a concentrated HIV epidemic among men who have sex with men (MSM) and the incidence and mortality rates are increasing, which is not the case globally. Stigma towards MSM is widespread and impedes HIV prevention and treatment efforts. Rapid Start ART (RS-ART) is an evidence-based practice that WHO, IAS, and Malaysia's Ministry of Health endorse, but it has not been studied in MSM. This grant proposal is a comprehensive fellowship training program focused on HIV prevention and stigma reduction, particularly among MSM. The fellowship, underpinned by the applicant's background in public health and biostatistics, aims to develop and implement RS-ART as an innovative Behavioral Design Interventions (BDIs) for effective stigma reduction. Central to this are three specific aims: Firstly, the identification of facilitators and barriers to the implementation of BDIs targeting HIV prevention among MSM using asynchronous online focus groups. The findings of this aim will be used to tailor an existing RS-ART protocol to MSM in particular. Secondly, the project with facilitate the introduction of RS-ART, an approach informed through training in NIATx implementation facilitation. Lastly, the program focuses on advancing dyadic analysis techniques to better understand the relational dynamics between healthcare providers and patients, aiming to reduce stigma and improve health outcomes. The fellowship's training component is multidisciplinary, encompassing stigma, implementation science including NIATx, and dyadic analysis. Planned activities include coursework, mentorship, and hands-on research, with a substantial component conducted in Malaysia, providing a unique international perspective and practical experience in diverse healthcare settings. This fellowship represents a critical step in the applicant's career trajectory towards becoming an independent researcher, with long-term goals centered on the development and implementation of high- impact stigma-reduction interventions for marginalized groups. The training and research conducted during this fellowship will contribute significantly to the fields of HIV prevention, stigma reduction, and public health implementation science, with a focus on addressing health disparities in low-income and marginalized communities.