PROJECT SUMMARY Cardiovascular disease (CVD) continues to disproportionally impact sexual and gender minorities (SGM) compared to non-SGM. Further, because young SGM engage in harmful cardiometabolic health behaviors (CHB; i.e., dysregulated sleep, physical inactivity, tobacco use, and alcohol use) and experience poorer mental health at higher rates than non-SGM, interventions are necessary to reduce harmful CHB and poor mental health before CVD occurs. A key social determinant of harmful CHB and poor mental health among SGM is exposure to racial, sexual orientation, and gender discrimination. However, as young people are spending more of their time online, there is a clear gap in our current understanding of how discriminatory features (e.g., racial discrimination) of frequented online spaces influence harmful CHB and mental health among SGM. Further, there is an unmet need to understand the role of protective factors (e.g., online community support) in the association between online discrimination and CHB and mental health. Therefore, to create culturally relevant CVD prevention interventions for SGM, we must first understand the ways in which discrimination is experienced in relevant online spaces (e.g., social media) and how this, in turn, is associated with CHB and mental health. The proposed work builds on research delineating the multiple environments at which individuals can experience discrimination, including in physical (e.g., perceived discrimination) and online (e.g., a racist post on Twitter) environments. This interdisciplinary team includes a collaboration with the National Internet Observatory (NIO) to understand individual-level exposure to discrimination in online spaces as well as exposure to discriminatory online sentiment tied to the places SGM frequent using sentiment analysis with Twitter data matched to GPS activity spaces method over a 30-day study period. Results of this study will distill the precedents and characteristics of the online environments defining the association between discrimination and harmful CHB and mental health among SGM. Specifically, this study aims to evaluate; 1a) the association between direct daily exposure to online discrimination based on race, sexual orientation, and gender in one’s social media feed and harmful CHB among diverse SGM; 1b) the association between exposure to place based discriminatory climate and harmful CHB among SGM; 2) the association between online discrimination and place based discriminatory climate on daily mood and stress; and 3) social protections (e.g., online support) that mitigate the association between exposure to individual level social media discrimination, harmful CHB, mood and stress among SGM. This study is innovative as it uses novel multi-level measurement of online discrimination, social protections, and CHB among diverse young SGM, who are historically underrepresented. The significance of this work includes the creation of tailored harmful CHB interven...