Background: In the 10th revision of the International Classification of Diseases and Related Health Problems (ICD-10), chronic pain was not represented adequately. Pain was left undefined and not recognized as a biopsychosocial phenomenon. Instead, a flawed dualism between psychological and somatic factors was implied. Individual diagnoses were ill-defined and scattered randomly through different chapters. Many patients received diagnoses in remainder categories devoid of meaningful clinical information. Method: The International Association for the Study of Pain launched a Task Force to improve the diagnoses for the 11th revision of the ICD and this international expert team worked from 2013-2019 in cooperation with the WHO to develop a consensus based on available evidence and to improve the diagnoses. Results: A new chapter on chronic pain was created with a biopsychosocial definition of pain. Chronic pain was operationalized as pain that persists or recurs longer than three months and subdivided into seven categories: Chronic primary pain and six types of chronic secondary pain. All diagnoses were based on explicit operationalized criteria. Optional extension codes allow coding pain-related parameters and the presence of psychosocial aspects together with each pain diagnosis. Conclusion: First empirical studies demonstrated the integrity of the categories, the reliability, clinical utility, international applicability and superiority over the ICD-10. To improve reliability and ease of diagnosis, a classification algorithm is available. Clinical psychologists and other clinicians working with people with chronic pain should watch the national implementation strategies and advocate for multimodal and interdisciplinary treatments and adequate reimbursement for all providers involved.