Obsessive-compulsive disorder is a severe and debilitating psychiatric disorder affecting more and more people worldwide. As the fourth most common psychiatric disorder, its history can be traced back to the 16th century. Although previously classified as an anxiety disorder in DSM-IV, it has recently been given its own chapter with related disorders in DSM-5. In ICD-10, OCD is grouped with neurotic, stress-related and somatoform disorders, and given the code F42. ICD-10 subdivides OCD into three types: predominantly obsessive type, predominantly compulsive type, and the most commonly found mixed type. Obsessions can be defined as repetitive and persistent thoughts or feelings that are viewed by the patient as intrusive and inappropriate and cause marked anxiety or distress. Typical obsessions include: fears of being contaminated by germs or poisons, fears of causing harm to oneself or others, and fears of committing some unacceptable action. Compulsions, on the other hand, are repetitive acts or behaviours that the patient deems necessary to perform as a response to an obsession, and which serve to reduce anxiety. Common compulsions include: excessive washing and cleaning, checking, seeking reassurance, hoarding objects, and insisting that things be put in a specific order or pattern. Based on the severity of symptoms OCD can be divided into mild, moderate and sever forms. Many theories exist on the etiology of OCD, but no theory is regarded as the sole etiologic factor. Comorbidity with other psychiatric disorders is common, with a lifetime history of major depression present in two thirds of OCD patients. An array of different psychiatric and neurologic disorders must be taken into account in the differential diagnosis of OCD such as: specific phobias, major depressive disorder, trichotillomania, hoarding disorder, tic disorders, and obsessive-compulsive personality disorder. The primary goal of treatment in the majority of OCD cases is to have the individual control the disorder rather than the obsessional disorder control the individual. Safe and effective first-line treatment for OCD includes cognitive-behavioural therapy (CBT) and pharmacotherapy with selective serotonin reuptake inhibitors (SSRIs). Severe and drug-resistant cases can be managed with electroconvulsive therapy and rarely, surgery. The course of the disease is chronic, and the quality of life largely depends on the severity of symptoms and the response to therapy.