AbstractBackgroundExcess weight is convincingly associated with several cancers, but the association with ovarian cancer is insufficiently clarified, in particular regarding subgroups defined by menopausal status and ovarian cancer histologic type.AimsWe carried out a comprehensive systematic review and meta‐analysis of overweight and obesity in relation to ovarian cancer with focus on different subgroups.Methods and ResultsWe searched PubMed and Web of Science for relevant cohort and case–control studies published from inception to June 2021 in English language and using a clear definition of overweight and obesity. We combined maximally adjusted risk estimates using a random effects model. We analyzed data from 15 cohort and 26 case–control studies, including 28 471 ovarian cancer cases. The relative risk of ovarian cancer for overweight and obesity was 1.06 (95% confidence interval [CI] = 1.00–1.12) and 1.19 (95% CI = 1.11–1.28), respectively. Among premenopausal women, increased ovarian cancer risk was noted for overweight (RR 1.34; 95% CI = 1.03–1.75) and obesity (RR 1.51; 95% CI = 1.21–1.88). By comparison, among postmenopausal women no statistically significant association was found for overweight (RR 1.00; 95% CI 0.87–1.14) and obesity (RR1.03; 95% CI = 0.82–1.31). Increased risk was found for mucinous (RR 1.44; 95% CI = 1.03–2.01) and clear cell (RR 1.82; 95% CI = 1.11–2.99) ovarian cancer subtypes, but not for serous (RR1.12; 95% CI = 0.84–1.50;) and endometroid subtypes (RR1.24; 95% CI =0.96–1.60).ConclusionsObesity is associated with increased ovarian cancer risk. That relation is largely due to a positive association between adiposity and ovarian cancer among premenopausal but not postmenopausal women and among cases with mucinous and clear cell but not serous or endometrioid histology.