PROJECT ABSTRACT There is 18.1% HIV prevalence for men who have sex with men (MSM) in South Africa and less than 10% of HIV-positive MSM are optimally adherent to antiretroviral treatment (ART). These outcomes are consistent with findings for MSM across sub-Saharan African settings where only a quarter are virally suppressed due to suboptimal ART adherence. Further, at least one-third of new HIV infections for MSM occur within primary partnerships, driven by higher rates of condomless anal intercourse with main partners, lower levels of HIV testing among partnered men, and the desire to create trust and intimacy through condomless sex. MSM often lack skills in communicating and managing their HIV treatment and prevention with existing and new partners. Studies indicate that uptake of HIV prevention is lower within established relationships and emerging evidence indicates that inaccurate knowledge about viral suppression is reducing the impact of Undetectable = Untransmittable (U=U) strategies. To improve HIV outcomes for partnered MSM, our preliminary work identified preferences for an intervention to include smartphones with video-chat and group-based interventions focused on skill-building in HIV stress, disclosure and treatment management while in relationships. Given these findings, we identified one evidence-based intervention?Healthy Relationships (HR)?to adapt and pilot-test to assess feasibility for MSM in Eastern Cape, South Africa. This intervention improves self-efficacy in HIV disclosure risk assessment and safe sex practices. In our adaptation, we will integrate additional components of: U=U education, HIV disclosure management planning, and ART management in the home with video-conference (VC) delivery of HR, and VC check-in?s to support adherence behavioral changes. HR will be named MPowered in Relationships (MR) to reflect local voices through adaptation and the empowerment objective of intervention. In the first aim, we will adapt and assess usability of MR, integrating ADAPT-IIT phases and Human Centered Design. A community advisory board will be established to guide integration of Enhanced Components, linguistic considerations, preferences, and mHealth technical considerations for VC MR sessions and Group Check-In?s. In the second aim, we will pilot-test the feasibility of MR and its preliminary impact on behavioral and biomedical outcome measures, with a community-based sample of HIV-positive MSM who are 18 years of age or older, sub-optimally ART adherent, represent a range of relationship lengths, have HIV-negative or unknown status partner, and live in Eastern Cape. We will determine feasibility (feasibility, acceptability, willingness, safety, cost), and the preliminary impact on mediators of HIV prevention and disclosure, ART adherence, and viral load. These outcomes will inform a larger R01 clinical trial powered to measure the efficacy of MR to create gains in ART adherence for partnered MSM in South Africa, a group critically overlooked in HIV programming and research.