Project Summary/Abstract Objective: The proposed study explores mediators and moderators of discrimination’s damaging effects on sleep. Background: Millions of Americans have sleep problems that undermine health, social and work functioning, and ultimately cost billions annually. Hence, understanding factors that hinder sleep is critical for personal and societal health. One factor hindering sleep is discrimination. Racial discrimination increases arousal, which disrupts sleep and contributes to health disparities between Black and White Americans. Significance: Although discrimination and sleep problems are consistently linked, little is known about the processes underlying this relation. Risk factors that lead to greater discrimination and consequently poorer sleep are also unclear. Innovation: Prior studies linking discrimination and sleep have not considered socioemotional processes, moderating conditions, and typically use cross-sectional self-report methods. By integrating daily, in vivo ecological momentary assessments of discrimination and emotion invalidation with objective sleep measures (i.e., actigraphy), the current work identifies processes underlying the crisis in race- based sleep disparities. Specific Aims: With a Black American sample, the proposal tests whether discrimination triggers emotion invalidation, termed social pain minimization (SPM), which negatively affects sleep and whether these effects are largest for individuals that strongly active Black racial stereotypes in others (i.e., Black racial phenotypicality; BRP). Expected Results: Within-participant experiences with discrimination are predicted to increase SPM and sleep problems. SPM is hypothesized to partially mediate the effect of discrimination on sleep. Finally, participants higher in BRP are expected to experience more discrimination and consequently worse sleep than those lower in BRP. SPM is predicted to more strongly mediate discrimination’s effect on sleep for those high (v. low) in BRP. Future Directions: The proposed work identifies intervening processes and risk factors for the discrimination—sleep relation, these relations can then be targeted by future interventions geared at fostering emotion validation to mitigate SPM’s corrosive effect on sleep.