The International classification of diseases (ICD) is the global standard for the diagnosis, treatment, research, and statistical reporting of health conditions, including mental and behavioral disorders. This entry provides a basic description of the ICD with regard to practice and research in clinical psychology and related disciplines. A brief overview summarizes the history of the ICD and its section on mental and behavioral disorders. Next, separate sections describe the full ICD‐10 system, the Clinical descriptions and diagnostic guidelines, the Diagnostic criteria for research, and other related resources. Similarities and differences between the ICD and the Diagnostic and statistical manual of mental disorders (DSM) are examined. Finally, the entry concludes with a discussion of the current usage, impending changes, and future directions for the ICD within the context of global mental health care.