Rosai-Dorfman disease (RDD) is a benign proliferative histiocytic disorder of unknown etiology, which typically manifests as lymphadenopathy and systemic symptoms. Lymph node involvement is typical, but soft tissue RDD without nodal or systemic involvement is extremely rare. We report on a case of soft tissue RDD in a 16-year-old girl with a palpable mass on her buttock. It was firm, mobile, and discrete without tenderness. Excisional biopsy was performed, then RDD was confirmed histologically. RDD is a non-neoplastic disease that should be considered in the differential diagnosis of other soft tissue tumors. While the optimal treatment for extranodal RDD remains controversial, surgical excision is typically curative.