The tzaousios () was a late Byzantine military office, whose exact functions and role are somewhat unclear. The term is derived from the Turkish çavuş, meaning "courier" or "messenger", and was in use by the Byzantines perhaps as early as the late 11th century. In the 13th–15th centuries, it became applied to officers serving in provincial posts. A tzaousios could serve as commander of the garrison of a kastron (a fortified administrative center run by a kephale), possibly combining the military and administrative roles, or as an officer to the megala allagia of the imperial field army. Most of the tzaousioi mentioned in the sources came from the Byzantine Morea, where they played an important role in provincial administration. In Macedonia and Thrace by contrast, they seem to have been li