A 40-year-old woman with a history of a growing erythematous nodule in the umbilicus was diagnosed histopathologically with endometriosis. This umbilical endometriosis occurred spontaneously without any previous surgical procedures. The lesion was partially removed surgically; she then entered menopause with a spontaneous involution of the residuum during the following months so that further invention was not required. Umbilical endometriosis is very rare with an estimated incidence of 0.5 to 1% of all patients with endometrial ectopia. As the clinical appearance of umbilical endometriosis may share features with a variety of other disorders, we discuss the clinical picture and differential diagnostic considerations in detail.