Primary malignant melanoma of the oral mucosa is rare and has scarcely been reported in patients from Latin America. The most frequently affected sites include the palate and gingiva of the maxilla. In this report, we describe primary malignant melanoma in a Latin American patient. A 3 × 3.5-cm black tumor was observed on the upper left retromolar area. The lesion exhibited a sessile base, irregular edges, soft consistency, and pain on palpation. Immunohistochemistry staining results were positive for S100 and HMB-45; the Ki-67 index was 20%. Contrast tomography of the skull, face, abdomen, and thorax, as well as ultrasound of the liver, did not reveal metastatic lesions. The patient underwent wide surgical excision of the lesion, followed by radiotherapy; he was subsequently rehabilitated with a somato prosthesis.