Histiocytic sarcoma (HS) is an exceedingly rare hematologic malignancy that typically presents in the skin, gastrointestinal tract, and lymph nodes. Few cases of HS have been reported in the head and neck. We describe the case of a two-year-old girl presenting with two weeks of left lower eyelid swelling. Diagnostic testing and biopsy revealed a large inferior orbital mass causing severe bony destruction with extension into the sinuses. Pathologic analysis revealed classic features of histiocytic sarcoma. To the best of our knowledge, no previous case of histiocytic sarcoma occurring in the orbit of a child has been reported. We present an exceedingly rare case of histiocytic sarcoma in a young child presenting with eyelid swelling.