Purpose of Review <p>Healthy sleep is crucial for overall well-being, yet disparities impacting racially and ethnically minoritized groups, sexual and gender minorities (SGM), individuals with disabilities, individuals of low socioeconomic status, and residents of underserved rural and disadvantaged neighborhoods persist. These disparities stem from socially patterned sleep determinants across socioecological levels, reflecting the downstream consequences of structural inequities. While literature on the social determinants (e.g., social and built environmental factors such as psychosocial stressors or noise pollution, respectively) of sleep is growing, few studies have clarified the mechanisms of these disparities by assessing these determinants as contributors or explanatory factors for these unjust population differences. Thus, this narrative review synthesizes seminal studies on determinants of sleep disparities by first articulating the state of the literature on populations impacted by sleep disparities and then highlighting studies that formally examined contributors to sleep disparities. We also highlight intervention, policy, and clinical strategies aimed at addressing determinants of sleep disparities to advance sleep equity.</p> Recent Findings <p>There is an emerging body of research that applies theory and socioecological frameworks to assess multi-level determinants of sleep disparities. Studies using mediation analyses support the roles of discrimination, chronic stress, and neighborhood disadvantage in racial and ethnic sleep disparities. For SES disparities, psychological distress, health conditions, and work-related stressors were highlighted as potential mediators via sequential modeling. Evidence of sleep disparities impacting other adversely affected populations is developing; however, studies on the underlying mechanisms of disparities are comparatively limited for SGM individuals, residents of rural and underserved communities, and people with disabilities. Interventions targeting social determinants are increasing, with some showing promise in reducing stress, improving access to diagnosis and treatment of sleep disorders, and cultural inclusion in intervention programming. Policy efforts such as later school start times, wage increases, and noise regulation were identified as upstream structural or community-level changes that could improve sleep equity. In clinical settings, we highlight that the inclusion of social needs screening, longer visit times, and community health workers may enhance access and trust. While promising, these strategies require further evaluation and adaptation to the sleep context, respectively, to effectively eliminate sleep disparities.</p> Summary <p>Sleep disparities are understood to result from inequities in micro-, meso-, and macro-level social determinants. While there is emerging empirical evidence that specific social determinants may partially explain racial, ethnic and SES disparities, research remains limited for other affected groups (e.g., SGM individuals, residents of rural communities). Within this limited sleep disparity mechanisms literature, studies often emphasize self-reported or single dimensions of sleep. Thus, further research leveraging theory and robust mediation analyses is needed to identify contributors to disparities in other sleep outcomes (e.g., sleep architecture, sleep apnea severity, and multidimensional sleep health) and to address gaps for lesser-studied groups. This review underscores the need to address multi-level determinants through tailored interventions, policymaking, and equity-focused clinical strategies to reduce sleep disparities among disproportionately impacted and underserved groups. By synthesizing current gaps and promising directions, our goal is that this narrative review serves as a blueprint for advancing sleep equity through rigorous, theory-informed research and coordinated action across sectors</p>