The vestiarion (Greek: βεστιάριον, from Latin: vestiarium, "wardrobe"), sometimes with the adjectives basilikon ("imperial") or mega ("great"), was one of the major fiscal departments of the Byzantine bureaucracy. In English, it is often known as the department of the Public Wardrobe. Originating from the late Roman palace office of the sacrum vestiarium, it became an independent department in the 7th century under a chartoularios. By the late Byzantine period, it had become the state's sole treasury department. The public vestiarion must not be confused with the Byzantine emperor's private wardrobe, the oikeiakon vestiarion, which was headed by the prōtovestiarios.
The bureau of the sacrum vestiarium (Latin for "sacred wardrobe") is first attested as one of the scrinia under the comes sacrarum largitionum in the 5th century, and was then headed by a primicerius. In the 7th century, as the old Roman departments were broken up, the sacrum vestiarium and the bureaus of the scrinium argenti and scrinium a milarensibus, which supervised the mints, were combined to form the department of the vestiarion, under the chartoularios tou vestiariou (χαρτουλάριος τοῦ βεστιαρίου). This official is variously known in the sources also as vestiarios (βεστιάριος) and [epi tou] vestiariou ([ἐπὶ τοῦ] βεστιαρίου). The office of vestiariou, attested in the late 13th and 14th centuries by George Pachymeres and Pseudo-Kodinos, however, was apparently a distinct and independent office, which function as the paymaster of the naval ships and apparently corresponds to that of "prefect of the army" (ἔπαρχος τοῦ στρατιωτικοῦ) attested in the 6th century as army paymasters.
The vestiarion functioned parallel to the other state fiscal departments, the sakellion and the various logothesia, and was responsible for minting coin and bullion, as well as the maintenance of imperial arsenals in Constantinople and the provisioning of the imperial fleet and army. In effect, the vestiarion functioned parallel to the sakellion; salaries for instance were paid one half by each department. In the 12th century, the vestiarion became the sole state treasury, and was commonly referred to simply as the tameion ("treasury"). As such it survived into the Palaiologan period, when its chairman (prokathēmenos) was in charge of "revenue and expenditure".
The information on the department's internal structure during the middle Byzantine period (late 7th-11th centuries) comes primarily from the Klētorologion of Philotheos, a list of offices compiled in 899. Under the department head, the chartoularios tou vestiariou entails: