Praetorian prefecture of Illyricum

Praetorian prefecture of Illyricum Praefectura praetorio per Illyricum Ἐπαρχότης Ἰλλυρικοῦ
Praet. prefecture of the East Roman Empire
347–630's
The praetorian prefecture of Illyricum (375–379)
Capital	Sirmium, later Thessalonica
Historical era	Late antiquity
• Established	347
• loss of most of Illyricum to Slavic incursions	630's
Political subdivisions	Diocese of Macedonia Diocese of Dacia Diocese of Pannonia (until 379)

The praetorian prefecture of Illyricum (Latin: praefectura praetorio per Illyricum; Greek: ἐπαρχότης/ὑπαρχία [τῶν πραιτωρίων] τοῦ Ἰλλυρικοῦ, also termed simply the prefecture of Illyricum) was one of four praetorian prefectures into which the Late Roman Empire was divided.

The administrative centre of the prefecture was Sirmium (375–379), and, after 379, Thessalonica.^[1][2] It took its name from the older province of Illyricum, which in turn was named after ancient Illyria, and in its greatest expanse encompassed Pannonia, Noricum, Crete, and most of the Balkan peninsula except for Thrace.