The quaestura exercitus was a peculiar administrative district of the Eastern Roman Empire with a seat in Odessus (present-day Varna) established by Emperor Justinian I (r. 527–565) on May 18, 536.
Territorially, the quaestura exercitus contained the Roman provinces of Moesia Inferior and Scythia Minor, located in the lower Danube region, as well as the provinces of Cyprus, Caria, and the Aegean Islands (i.e. the Cyclades). All of these provinces were detached from the Praetorian prefecture of the East and placed under the authority of a new army official known as the quaestor exercitus ("Quaestor of the army"). The authority of the quaestor was the equivalent to that of a magister militum. Since the strategically vital Danubian provinces were economically impoverished, the purpose of the quaestura exercitus was to help support the troops that were stationed there. By connecting the lower Danubian provinces with wealthier provinces, Justinian was able to transport supplies via the Black Sea. This territorial restructuring relieved both the destitute populations and devastated countryside of the Danubian provinces from sustaining any stationed troops. Unfortunately, there is a lack of subsequent evidence on the history of the quaestura exercitus. However, since the position of quaestor was still existent during the mid-570s, this indicates that the overall territorial unit achieved a modicum of success.
Ultimately, the Danubian provinces associated with the quaestura exercitus did not survive the Slav and Avar invasions of the Balkans in the 7th century. However, isolated fortresses on the Danube delta and along the coast of the Black Sea were maintained via supplies by sea, and there is evidence that the great naval corps of the Karabisianoi was first formed by the remainders of the quaestura. Lead seals from Moesia Inferior and Scythia Minor provide evidence supporting the existence of the quaestura exercitus. Specifically, thirteen imperial seals (nine of which are from Justinian) demonstrate that communications between officials from Scythia Minor and Constantinople occurred on a somewhat regular basis.