ABSTRACT Black and Latino trans women and men who have sex with men – or sexual and gender minorities of color (SGMoC) - account for at least half of all new HIV infections in the United States (U.S.). At the same time there is a significant disparity in knowledge of, access to and uptake of pre-exposure prophylaxis (PrEP) among SGMoC is disproportionately low compared to white MSM and trans women. Numerous studies have articulated disparities in HIV among groups under the SGMoC umbrella. However, most research aggregates experiences based on one axis of stigma such as gay or trans identity. Intersectional HIV stigma, or stigma as the result of multiple, intersecting minority identities, offer a complex lens in which to examine the multiplicative effect of experiencing more than one axis of stigma. SGMoC face stigma as sexual, gender and racial/ethnic minorities. SGMoC with these intersecting identities face racism, sexism, transphobia and a host of other stigmas that put them at high risk of HIV and create barriers to HIV prevention. This study will include a 3-year in-depth longitudinal qualitative phase, a 12-month longitudinal social epidemiologic phase, and an intensive longitudinal ecological momentary assessment phase. We propose to use an innovative and culturally relevant sampling strategy of web-based respondent driven sampling (webRDS) to recruit an online cohort of 900 SGMoC. The online cohort will complete 3 survey assessments in six-month intervals. The 200 highest risk cohort participants will participate in EMA phase with to measure the immediate context of intersectional HIV stigma, HIV prevention behaviors and HIV risk. These participants will receive short random ecological momentary assessments daily for 30 days via a mobile health application. Not only will this study examine intersectional HIV stigma in context of the daily lives of SGMoC, the ecological momentary assessment phase will also inform future development of a context aware, ecological momentary intervention to reduce intersectional HIV stigma and optimize the HIV prevention and care continua.