Ovarian cancer is the most common fatal gynecological malignancy, but its incidence in the general population is low. Due to the lack of effective prevention or early detection approaches and the late clinical presentation, most ovarian cancers are detected at advanced stages with poor outcomes, and risk factors are not well characterized. The Ovarian Cancer Cohort Consortium (OC3) was initiated through the National Cancer Institute Cohort Consortium in 2010 to address the need for well-powered prospective studies with ovarian cancer endpoints. The OC3 is an international consortium of cohort studies and provides a unique resource to conduct studies of ovarian cancer risk factors, biomarkers, risk prediction, and outcomes while accounting for ovarian cancer subtypes.