We report the case of a 53-year-old man with a solitary nodule located on the inner surface of the prepuce. The lesion was removed and the final diagnosis was Rosai-Dorfman disease (RDD/sinus histiocytosis with massive lymphadenopathy). This report, being the first case of RDD presenting as a single nodule of the penis, broadens the spectrum of the cutaneous expression of RDD.