Inflammatory Optic Neuritis (ON) is the most frequent cause of acute visual loss in young adults. Although the visual prognosis is excellent in the majority of cases, many patients develop pathology, such as multiple sclerosis, in its subsequent evolution. The natural history of ON has been studied in numerous works in recent years; one of the most important of which is Optic Neuritis Treatment Trial. Magnetic Resonance plays a fundamental role in the etiological diagnosis of ON and in predicting the risk of conversion into multiple sclerosis. New exploratory techniques have recently been incorporated, such as optical coherence tomography, useful for diagnosis and prognosis; serum biomarkers have been identified in the diagnosis of other pathologies with an autoimmune nature that produce ON. A better understanding of the clinical and exploratory data of typical ON will make a more rapid and accurate diagnostic study possible. Treatment of ON with steroids must be individualised bearing in mind that they do not alter the long-term prognosis and an immunomodulating therapy must be proposed for patients with a high risk of conversion into multiple sclerosis. This article reviews the existing data in the literature on its clinical manifestations, its etiological and differential diagnosis, and the treatment of inflammatory ON.