We report a unique case of Rosai-Dorfman disease (sinus histiocytosis with massive lymphadenopathy) involving the uterus. A 63-yr-old female with a history of parathyroid adenoma and cavernous sinus meningioma underwent total abdominal hysterectomy for a possible uterine malignancy. The histologic findings consisted of a nodular, mass-like infiltration of the myometrium by clusters, cords, and sheets of CD163-positve, S100-positive histiocytes with lymphocytophagocytosis (emperipolesis). The cells were negative for CD1a and langerin. Occasional plasma cells and erythrocytes were also present. Most of the histiocytes had pale, vacuolated, or foamy cytoplasm. In all cases, the nuclei were small and eccentric. No mitotic figures were identified. Two prior cases of Rosai-Dorfman disease have been reported in the female genital tract: 1 in the cervix and 1 in the bilateral ovaries. Rosai-Dorfman disease should be added to the differential diagnosis of histiocyte-rich lesions in the female genital tract. The diagnosis should be strongly considered in the presence of the characteristic histology with lymphocytophagocytosis (emperipolesis). A limited immunohistochemical panel consisting of CD163, S100, and CD1a and/or langerin will confirm the diagnosis in most cases.