Medication overuse headache (MOH) is a globally prevalent and debilitating condition that results from excessive use of acute therapies and can significantly affect quality of life, despite the fact that simple information about the causes and consequences of the condition can help prevent or stop MOH. In recent years, many new insights have been gained into headaches caused by medication overuse. In addition, the diagnostic criteria and guideline recommendations have changed considerably. This article provides a comprehensive overview of the clinic, definition/classification, epidemiology, risk factors, pathophysiology, controversies, prevention, and treatment of MOH.