Lichen planus is a common, chronic, inflammatory, immunologically-mediated dermatomucocutaneous lesion. The name was coined by Erasmus Wilson in 1869, and the oral form is more common than the cutaneous lesion. Significantly, oral lesions can occur independently of skin lesions. While oral lesions are generally asymptomatic, the atrophic and erosive forms of lichen planus can cause a range of symptoms, from spontaneous soreness to severe pain that interferes with eating, speech, and swallowing. Managing oral lichen planus is challenging due to its chronic nature, which requires long-term anti-inflammatory and immunomodulatory therapy. The cell-mediated reaction resulting in oral lichen planus may be precipitated by a wide range of factors, including several infective agents such as viruses and Helicobacter pylori. Herpes, Epstein-Barr virus, cytomegalovirus, and herpes virus-6 have all been implicated as causative agents for lichen planus. A variety of medications can induce lesions similar to the idiopathic form of lichen planus, and this is called lichenoid mucositis or lichenoid dermatitis. Lichen planus may also be associated with hepatitis C infection, and genetic influences may play a role in its expression in certain populations. Stress or anxiety related to the lesion may also be noted.