Background: Congenital red blood cell (RBC) disorders, such as hemoglobinopathies, are frequent worldwide but with large geographical variation. Growing migration has increased the number of patients with RBC disorders in formerly low prevalence countries, eg, Denmark. However, accurate prevalences are unknown. Methods: Patients with a registered diagnosis of congenital hemolysis in the Danish National Patient Register between 1977 and 2016 were linked to a national laboratory database of RBC disorders and the Danish civil registration system. We calculate annual age-and sex-specific prevalences of the congenital hemolytic disorders from 2000 to 2016. Results: Prevalences of all subtypes of congenital hemolytic disorders increased during the study period. The prevalence of hereditary spherocytosis increased 1.73 times between 2000 and 2015, from 10.2/105 persons to 17.7/105 persons. Alpha thalassemia trait had a prevalence of 0.5/ 105 persons in 2000, but increased 41 times to 19.2/105 persons in 2015. Beta thalassemia minor increased eightfold from 4.5/105 persons in 2000 to 34.9/105 persons in 2015. Likewise, sickle cell trait increased 11 times from 0.7/105 persons in 2000 to 8.1/105 persons in 2015, whereas sickle cell disease increased from 0.5/105 persons to 2.7/105 persons in 2015, a fivefold increase. Conclusion: The prevalence of congenital RBC disorders in Denmark is increasing. The hemoglobinopathy traits now have prevalences as high as hereditary spherocytosis. These estimates of congenital hemolytic disorders in Denmark emphasize that inborn hemoglobin disorders are a public health concern, even in some formerly low prevalence countries.