The original
Roman mint network was reorganized and centralized by Emperor
Diocletian () at the end of the 3rd century, parallel to the restructuring of the Roman Empire's
provincial and
fiscal administration. The mints were limited to one per
diocese (except for a few exceptions) and placed under the dual control of the
praetorian prefectures and the
comes sacrarum largitionum. During the next two centuries, some mints were closed and others opened as fiscal necessity or administrative changes dictated. In addition, the various emperors had mints attached to their retinue (
comitatus) which followed them on their journeys and campaigns throughout the
Roman Empire. After a law promulgated in 366/369, the minting of precious-metal coins was confined to these comitatensian mints, operating either from a permanent base or by making use of the regional mints nearest to the current location of the emperor and his
comitatus. Otherwise, regional mints were mostly limited to issuing base-metal coins. During the course of the 5th century, the Roman minting system collapsed. The
western half of the Roman Empire was overrun by
Germanic tribes, although some mints remained active in the West under the new barbarian rulers and continued to mint coins, including high-quality gold
solidi, in the name of the eastern emperors, most notably in
Ostrogothic Italy and
Burgundy. In the
East, most mints seem to have been active until some time into the reign of
Zeno (), but by the accession of
Anastasius I () only the mints of
Constantinople and
Thessalonica remained active. In 498, Anastasius initiated a major coinage reform—carried out by the
comes sacrarum largitionum John the Paphlagonian—which is held to mark the start of the
"Byzantine" coinage system proper. At the same time, he re-opened the mints at
Nicomedia and later at
Antioch. The number of mints expanded greatly during the reign of
Justinian I (), in large part due to his reconquest of
Italy,
Africa, and
parts of Spain. As many as fourteen mints were active during Justinian's reign, with new mints opened or taken over from the
Vandals and
Ostrogoths in
Carthage,
Rome,
Ravenna,
Carthagena, and in smaller provincial centres. Most of these were confined to
copper coinage. Ravenna and Carthage alone produced silver coins in quantity, while gold issues were restricted to
Catania, Thessalonica, and Constantinople; the latter two cities, however, far outstripped the others in output. The territorial losses of the early 7th century, with the
Byzantine–Sassanid War of 602–628, the
Slavic incursions into the
Balkans, and the onset of the
Muslim conquests, drastically diminished the number of active mints. In 628/629, Emperor
Heraclius () closed all remaining provincial mints in the East except for
Alexandria, which
fell to the Arabs in 641. In the West too, one by one the cities hosting the various mints fell to various enemies, until by the 9th century, only
Syracuse remained. With the
fall of Syracuse in 878,
Constantinople remained the sole mint for gold and silver coinage until the late 11th century. The provincial mint at
Cherson was reopened c. 860, but its output was restricted to copper coinage. Thessalonica became the main provincial mint after it reopened in the second half of the 11th century, and other provincial centres—
Thebes or
Corinth in southern
Greece,
Philadelphia in the 14th century,
Magnesia and
Nicaea during the
Empire of Nicaea (1204–1261)—were active at times during the Byzantine Empire's last centuries. Usurpers or semi-autonomous local lords also occasionally established mints of their own, like
Isaac Komnenos of Cyprus,
Leo Gabalas of
Rhodes, or the
Gabras family of
Trebizond. Constantinople, however, remained the main mint, providing the bulk of the coinage. ==List (principal mints in bold)==