Thepraetorian prefecture (Latin:praefectura praetorio; inGreek variously namedἐπαρχότης τῶν πραιτωρίων or ὑπαρχία τῶν πραιτωρίων) was the largestadministrative division of thelateRoman Empire, above the mid-leveldioceses and the low-levelprovinces. Praetorian prefectures originated in the reign ofConstantine I (r. 306–337), reaching their more or less final form in the last third of the 4th century and surviving until the 7th century, when the reforms ofHeraclius diminished the prefecture's power, and theMuslim conquests forced theEastern Roman Empire to adopt the newtheme system. Elements of the prefecture's administrative apparatus, however, are documented to have survived in theByzantine Empire until the first half of the 9th century.

The office of thepraetorian prefect had a long history dating back to the origins of theRoman Empire: initially, its two holders were the commanders of thePraetorian Guard, but gradually, they became the emperor's chief aides, and amassed considerable administrative and judicial responsibilities. The exact process of transformation to the chief civilian administrator of a specific territorial circumscription is still unclear.^[1] A common misconception, based onZosimus, is thatConstantine I established the praetorian prefectures as definite territorial administrations as early as 318, or in 324, after his victory overLicinius.^[2]

During theTetrarchy, when the number of holders of the imperial office multiplied (two senior emperors, theAugusti, and two junior colleagues, theCaesares), there is evidence for the existence of only two prefects at each time, presumably assigned to each of theAugusti. At that stage, the prefect's power was still immense. In the words ofA.H.M. Jones, he was "a kind ofgrand vizier, the emperor's second in command, wielding a wide authority in almost every sphere of government, military and judicial, financial and general administration. He was the emperor’s chief of staff, adjutant-general, and quartermaster-general...".^[3] FollowingDiocletian's abdication in 305, civil war erupted among the various co-emperors, during which time each of the contenders appointed his own prefect, a pattern carried on during the period where the Empire was shared betweenLicinius andConstantine I.^[4] In 317 a third prefect was added in Gaul for Constantine's sonCrispus. After his execution in 326 this prefect was retained. Thus, from 317 onwards, there were never less than three, and for years 347–361, 374–379 and 388–391, four, with the addition of aPraetorian prefecture of Illyricum, although in the last two years it comprised only the dioceses of Dacia and Macedonia which would be the permanent territory from then on after restoration in 395.

Following Constantine's victory over Licinius and the unification of the Empire under his rule, the office was transformed. The prefect's military duties were removed by the creation of the purely military offices of themagister peditum andmagister equitum ("Master of the Foot/Horse"), and the establishment of themagister officiorum as the powerful head of the palatine bureaucracy and the civil service at large provided a counterbalance to the prefect's power.^[5][6] These reforms were the result of both the lack of officials suitable for the prefect's wide-ranging tasks,^[7] and of the desire to reduce the potential challenge to the emperor's authority posed by the over-mighty prefect.^[8] The office of the prefect was consequently converted into a purely civilian administrative one, albeit retaining the highest position in the imperial hierarchy, immediately below the emperor himself.^[9] Another important departure from tetrarchic practice was the increase in the number of holders: no less than five prefects are attested for ca. 332. This development is likely related to Constantine's giving his four sons specific territories to administer, envisioning a partition of imperial authority among them following his death. In this, the origins of the later territorial prefectures may be detected.^[10]

After Constantine's death in 337, his three surviving sons partitioned the Empire between them. As each newAugustus had his own praetorian prefect, this division created the first of what would gradually become the permanent praetorian prefectures: the westernprefecture of Gaul (dioceses ofGaul, Viennensis,Hispania andBritain), the centralprefecture of Italy, Illyricum and Africa (dioceses ofItaly,Africa,Pannonia,Dacia andMacedonia) and theprefecture of the East (dioceses ofThrace,Asia,Pontus,Oriens). Egypt was part of the diocese of Oriens until 370 or 381. With the creation of the separateprefecture of Illyricum (dioceses ofPannonia,Dacia andMacedonia) in 347 until 361, and despite the occasional abolition of the latter, the picture that appears in the early 5th-centuryNotitia dignitatum ("list of dignities") was complete. The only major change was the removal of the diocese of Pannonia (renamed "Diocese of Illyricum") from the prefecture of Illyricum and its incorporation into the prefecture of Italy in 379. The diocese of Italy was in practice divided into two: of Italy in the north, and suburbicarian ("under theCity") Italy in the south including Sicily, Corsica and Sardinia. There were no vicars appointed to the dioceses of Gaul and Dacia, because the praetorian prefects of Gaul and Illyricum were resident. When the prefect of Italy was in Milan, a vicar for Illyricum was appointed to reside in Sirmium; when the prefect resided in Sirmium, the post was lapsed, and a vicar was appointed to reside in Milan in place of the prefect.

In the course of the 5th century, the Western Empire was overrun by theinvasions ofGermanic tribes. However, the prefecture of Italy was retained by the newOstrogothic Kingdom, which was stillde jure part of the Empire, and Ostrogothic kingTheodoric the Great even re-established the prefecture of Gaul in the small portion of Gaul he conquered in the 510s. After the reconquest of Northern Africa by the Eastern Empire during theVandalic War of 533–534, the new provinces were grouped by emperorJustinian I into a newpraetorian prefecture of Africa, which would later be transformed into theExarchate of Africa. Thepraetorian prefecture of Italy was also re-established after the end of theGothic War, before it too evolved into anexarchate. In the East, the prefectures would continue to function until the mid-7th century, when the loss of most eastern provinces to theMuslim conquest and of the Balkans toSlavic tribes led to the creation of theTheme system. In the meantime, however, reforms underHeraclius had stripped the prefect from a number of his subordinate financial bureaux, which were set up as independent departments underlogothetes.^[11] The last time the prefect of the East is directly attested comes from a law of 629.^[12] According to some scholars, however, traces of the system survived into the early 9th century: Ernst Stein demonstrated that some aspects of the Illyrian prefecture survived in the administration ofThessalonica,^[13] whileJohn Haldon, based onsigillographic evidence and references in the ByzantineTaktika, has documented the survival of the earlier civilian provincial administration within thetheme system, with the prefect in Constantinople possibly in a supervisory capability, until the 840s.^[14]

Originally, the praetorian prefects were drawn from theequestrian class. Constantine's reforms entailed the reservation of this office for members of the senatorial class, and its prestige and authority were raised to the highest level, so that contemporary writers refer to it as the "supreme office".^[16] In the divided Empire, the two senior prefects were those of the East and of Italy, residing in the courts of the two emperors and acting effectively as their first ministers, while the prefects of Illyricum and Gaul held a more junior position.^[17]

The prefects held wide-ranging control over most aspects of the administrative machinery of their provinces, and only themagister officiorum rivalled them in power. The prefects fulfilled the roles of supreme administrative and juridical official, already present from the time ofSeptimius Severus, and that of chief financial official, responsible for the statebudget. In their capacity as judges, they had the right to pass judgment instead of the emperor (vice sacra), and, unlike lower governors, their decision could not be appealed.

Their departments were divided in two major categories: theschola excerptorum, which supervised administrative and judicial affairs, and thescriniarii, overseeing the financial sector.^[18]

• Notitia dignitatum
• Bury, John Bagnell (1923).History of the Later Roman Empire, Volume I, Chapter II. Macmillan & Co., Ltd.
• Haldon, John F. (1997).Byzantium in the Seventh Century: The Transformation of a Culture. Cambridge University Press.ISBN 978-0-521-31917-1.
• Jones, A.H.M. (1964).The Later Roman Empire, 284-602: A Social, Economic, and Administrative Survey.
• Kazhdan, Alexander, ed. (1991).Oxford Dictionary of Byzantium. Oxford University Press.ISBN 978-0-19-504652-6.
• Kelly, Christopher (2006). "Bureaucracy and Government". In Lenski, Noel (ed.).The Cambridge Companion to the Age of Constantine. Cambridge University Press.ISBN 978-0-521-52157-4.
• Morrisson, Cécile, ed. (2007).Le Monde byzantin, tome 1: L'Empire romain d'Orient, 330-641 (in Greek). Athens: Polis Editions.ISBN 978-960-435-134-3.

• Praetorian prefectures
• Roman Empire in late antiquity

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