Modified Project Summary/Abstract Section Despite increased attention to couples-based HIV prevention strategies, interventions specifically designed for adult couples have not been rigorously evaluated in large-scale trials. The proposed study is a randomized controlled trial (RCT) of a couples-based HIV prevention intervention. The intervention builds on extensive formative research conducted by the investigative team, including remote delivery of study procedures and the use of objective biomarkers to assess adherence to HIV treatment and pre-exposure prophylaxis (PrEP). The intervention consists of three sessions grounded in social cognitive theory and a relationship-oriented ecological framework. It has demonstrated strong feasibility and acceptability in a pilot RCT, along with promising preliminary evidence of changes in targeted behavioral mechanisms. The intervention is innovative in that it: (1) integrates biomedical prevention strategies, including pre-exposure prophylaxis (PrEP) and treatment as prevention (TasP), with psychoeducational skill development; (2) provides clear and accessible information about HIV prevention and treatment options; (3) applies a prevention and treatment framework appropriate for couples regardless of HIV status; (4) uses a validated composite algorithm to assess HIV protection beyond condom use alone; and (5) addresses relational and contextual factors associated with HIV transmission risk. The primary objective is to determine whether participants assigned to the intervention condition demonstrate a greater proportion of HIV-protected sexual acts compared to those assigned to a time- and attention-matched Wellness Promotion control condition. HIV protection is defined using a validated composite measure that includes condom use, PrEP use, TasP, or a combination of these strategies to reduce risk of HIV transmission within and outside the primary partnership. The study will enroll 150 adult couples (N=300 individuals) from multiple U.S. jurisdictions with elevated HIV prevalence. Participants will complete follow-up assessments every three months over a nine-month period. Data collection will include biological measures (self-administered HIV testing and hair biomarkers for PrEP and antiretroviral therapy adherence), as well as behavioral and psychosocial assessments. The findings from this study will inform practical recommendations for broader implementation of evidence-based HIV prevention interventions. This trial will provide rigorous evidence regarding the efficacy of a scalable couples-based intervention designed to increase sustained HIV protection among adult male couples.