Epidermoid bone cysts are rare, unilocular, and slow growing. They develop by the accumulation of ectodermal remnants, and they may be congenital or acquired. The most common locations for these bone cysts are the distal phalanges, followed by the skull. This paper documents an adult male from the Islamic (twelfth and thirteen centuries CE) burial site of Ibi in the Province of Alicante, southeast Spain. This individual had a cranial lesion in the form of a roughly elliptical hole in the posterior fossa (left occipital region). The lesion was examined macroscopically and using X-ray photography. Based on the shape of the lesion, the most likely diagnosis would appear to be a benign tumour, a so-called "hourglass" epidermoid cyst. No direct link between this tumour and the cause of death can be established.