SUMMARY/ABSTRACT Transgender and non-binary (TGNB) persons experience intimate partner violence (IPV) at alarming rates twice that of their cisgender peers. Prior work has linked IPV to sexual risk behavior and increased risk for HIV seroconversion among TGNB, but less is known about the impact of IPV on HIV and sexually transmitted infection (STI) testing, pre- exposure prophylaxis (PrEP) uptake, and persistence among TGNB. While past findings suggest the potential for IPV to have a strong deleterious effect on HIV prevention continuum engagement, IPV experiences and impacts on HIV/STI risk and prevention behaviors have yet to studied among a diverse group of TGNB persons. Additional research is currently needed to model pathways between IPV and HIV risk for subgroups of trans feminine (TF), trans masculine (TM), and gender non-binary (GNB) persons. Guided by a framework that combines Syndemic and Minority Stress Theory, the proposed innovative observational cohort study will examine how specific forms of IPV (e.g., physical, sexual, emotional, controlling gender expression and/or transition) in the context of steady or casual intimate relationships contribute to HIV/STI risk and protective behaviors among subgroups of TGNB persons over a 24-month timeframe. Specifically, we aim to: 1. Using qualitative methodologies, explore the perceived associations between IPV, relationship characteristics and dynamics, and HIV risk and prevention behaviors among gender diverse TGNB persons. 2. Examine gender-based differences in the longitudinal associations of IPV with HIV testing, PrEP uptake, PrEP persistence, STI diagnosis (primary outcomes), condomless sex, and HIV seroconversion (secondary outcomes) among a racially and ethnically diverse cohort of TGNB persons (TF, TM, and GNB groups). 3. Determine the individual-, interpersonal-, network-, community-, and structural-level risk and resilience factors that mediate (or moderate) the associations between IPV and HIV risk and protective behaviors for each group. 4. Make recommendations for interventions that interrupt the pathways between IPV and HIV/STI risk based on quantitative data from the cohort and qualitative data, guided by technical experts. We will assess sexual risk behavior, conduct HIV and STI testing, and assess PrEP uptake and persistence over the 24 months of follow-up. We hypothesize that there will be differences in the frequency, severity, and overall impact of IPV on HIV/STI risk among subgroups of TGNB persons. We also suspect greater frequency of IPV will be associated with history of childhood abuse, mental health problems, substance use, sexual risk taking and lower levels of HIV testing, PrEP uptake, and PrEP persistence. We anticipate that alcohol and substance use among participants and their partners will be highly associated with episodes of IPV and with HIV risk behavior. We also hypothesize that experiences of gender affirmation, coping skills and social support will media...