The Health Equity Core focuses on one of the greatest US and global public health challenges in the persisting HIV epidemic – reducing inter-related inequities in (a) HIV prevention and care and (b) screening for treatment of mental health (MH), including substance abuse. MH problems are among the most significant barriers to achieving UNAIDS 95-95-95 targets. Remarkable advances have transformed HIV prevention and treatment; likewise, evidence-based interventions (EBIs) address a range of MH problems that are consistently associated with poor health outcomes; for example, delayed HIV diagnosis, poor engagement, and retention in care, and virologic failure. Nevertheless, disparities in accessing HIV services and MH services for HIV-affected populations (HIV-MH services) – and in the associated HIV continuum outcomes – persist among minoritized and marginalized populations and in resource-poor settings. Guided by perspectives such as intersectionality, equity and disparities, to enable the HIV Center to reach these goals, the Health Equity Core has the following Specific Aims: (1) to promote research to IDENTIFY disparities in HIV and HIV-MH prevention and care by applying behavioral and social science research that (a) prioritizes community-based designs and participatory research and (b) use innovative web-based technologies (e.g., geospatial, real-time, app-based) to the capture of multi-level data that identify and characterize disparities (Framework Phase 1); (2) to promote research to UNDERSTAND the intersecting impacts of social determinants of HIV and HIV-MH prevention and care disparities by (a) applying intersectionality, equity, and SDoH perspectives, (b) promoting use of implementation science equity frameworks to guide the measurement and analysis of patient, provider, and organizational factors such as reach, access, and sustainability in vulnerable populations, and (c) exploring the influence of intersecting epidemics (e.g., COVID-19, global crises), to improve HIV and MH systems preparedness (Framework Phase 2); and (3) to advance intervention and implementation science to REDUCE HIV and/or HIV-MH disparities through participatory approaches that (a) leverage digital technologies in interventions and implementation strategies to maximize equitable access to HIV and/or HIV-MH prevention and care and (b) tailor evidence-based multi-level interventions and implementation strategies, to address SDoH, including leveraging local wisdom and resources to facilitate rigorous and sustainable scale up of EBIs (Framework Phase 3).