Optic neuritis (ON) is defined as inflammatory optic neuropathy. In its initial clinical appearance, ON can have unilateral or bilateral manifestation and anterior (papillitis) or retrobulbar localizations. Traditionally, they are divided into typical and atypical ON. In the western hemisphere, most optic nerve inflammations are associated with multiple sclerosis, in their typical form. However, ON can be associated with a series of disorders of unknown or known origin. Atypical ON has a somewhat different clinical picture from typical and encompasses neuromyelitis optica spectrum disease (NMOSD), idiopathic recurrent neuroretinitis (NR), chronic relapsing inflammatory optic neuritis (CRION), ON within systemic autoimmune diseases, and neuritis during or after infectious diseases or vaccination. Their cause should be meticulously worked up, because of the therapeutic and prognostic challenges that they present.