Oral Lichen planus (OLP) is the most frequent mucosal localization of Lichen planus, affecting about 1-2% of the population. It is associated with skin lesions in 60-70% of cases, while occurring as the only manifestations in 15-25% of patients. Six clinical forms of OLP are identified: reticular (the most common), plaque, papular, atrophic, vesicles/bullous and erosive. The evolution is chronic, especially in the erosive form. A 1% incidence of squamous-cell carcinoma has been reported, thus considering OLP as a potential premalignant condition. The etiopathogenesis is still not completely understood: genetic (HLA-DR2), immunologic (T cell-mediated) and infectious (association with viral hepatitis C, differences in oral microbiota in OLP, and bacteria internalization into infiltrating T cells and oral epithelial cells) are considered the main predisposing or provoking factors. Management is based on the severity of the lesions; topical steroids are the first-line therapy and oral glucocorticoids are used for severe erosive lesions.