Objective: To characterize ovarian cancer patients who die within 6 months of diagnosis and to identify prognostic factors for these early deaths. Methods: A nationwide cohort study covering ovarian cancer in Denmark in 2005–2016. Tumor and patient characteristics including comorbidity and socioeconomic factors were obtained from the comprehensive Danish national registers. Results: A total of 5,570 patients were included in the study. Three months after ovarian cancer diagnosis 456 (8.2%) had died and 664 (11.9%) died within 6 months of diagnosis. Adjusted for age and comorbidity, patients who died early were admitted to hospital significantly more often in a 6-month period before the diagnosis (odds ratio [OR]=1.61 [1.29–2.00], and OR=1.47 [1.21–1.78]), for patients who died within 3 and 6 months respectively). Low educational level (OR=2.11), low income (OR=2.50) and singlehood (OR=1.90) were factors significantly associated with higher risk of early death. The discriminative ability of risk factors in identifying early death was assessed by cross-validated area under the receiver operating characteristic curve (AUC). The AUC was found to be 0.91 (0.88–0.93) and 0.90 (0.87–0.92) for death within 3 and 6 months, respectively. Conclusions Despite several admissions to hospital, the ovarian cancer diagnosis is delayed for a subgroup of patients, who end up dying early, probably due to physical deterioration in the ineffective waiting time. Up to 90% of high-risk patients might be identified significantly earlier to improve the prognosis. The admittance of the patients having risk symptoms should include fast track investigation for ovarian cancer.