BACKGROUND Discrimination promotes multisystem physiological dysregulation termed allostatic load, which predicts morbidity and mortality. It remains unclear whether weight-related discrimination influences allostatic load. PURPOSE The aim of this study was to prospectively examine 10-year associations between weight discrimination, allostatic load, and its components among adults 25-75 years in the Midlife Development in the US Biomarker Substudy. METHODS Participants with information on weight discrimination were analyzed (n=986). At both timepoints, participants self-reported the frequency of perceived weight discrimination across nine scenarios as "never/rarely" (scored as 0), "sometimes" (1), or "often" (2). The two scores were averaged and then dichotomized as "experienced" versus "not experienced" discrimination. High allostatic load was defined as having ≥3 out of 7 dysregulated systems (cardiovascular, sympathetic/parasympathetic nervous systems, hypothalamic pituitary axis, inflammatory, lipid/metabolic, and glucose metabolism), which collectively included 24 biomarkers. Relative risks (RR) were estimated from multivariate models adjusted for sociodemographic and health characteristics, other forms of discrimination, and BMI. RESULTS Over 41% of the sample had obesity, and 6% reported weight discrimination at follow-up. In multivariable-adjusted analyses, individuals who experienced (versus did not experience) weight discrimination had twice the risk of high allostatic load (RR, 2.07; 95 % CI, 1.21; 3.55 for baseline discrimination; 2.16, 95 % CI, 1.39; 3.36 for long-term discrimination). Weight discrimination was associated with lipid/metabolic dysregulation (1.56; 95 % CI 1.02, 2.40), glucose metabolism (1.99; 95 % CI 1.34, 2.95), and inflammation (1.76; 95 % CI 1.22, 2.54), but no other systems. CONCLUSIONS Perceived weight discrimination doubles the 10-year risk of high allostatic load. Eliminating weight stigma may reduce physiological dysregulation, improving obesity-related morbidity and mortality.