<p>Economic inequality is believed to negatively affect individuals’ psychological and physical health. We hypothesized that perceptions of greater economic inequality predict poorer sleep quality through social comparison and stress. We tested this hypothesis across three studies. Study 1 used a large-scale longitudinal dataset with a nationally representative sample in China (<i>n</i> = 37,984) to investigate the within-participant association between economic inequality and sleep quality over time. A fixed-effects model revealed that participants perceiving increasing economic inequality reported poorer sleep quality, whereas objective economic inequality did not predict sleep quality. Study 2 used a cross-sectional college sample (<i>n</i> = 668) and a cross-sectional community sample (<i>n</i> = 1,009) to replicate the findings and further examine psychological mechanisms underlying the relationship between perceived economic inequality and sleep quality. Structural equation models confirmed that higher perceived economic inequality was associated with poorer sleep quality. Moreover, in both samples, the relationship was sequentially mediated by upward social comparison and stress. These findings provide important insights into understanding the psychological and epidemiological implications of economic inequality.</p>