The Diocese of Pannonia (, lit. "Diocese of the Pannonias"), from 395 known as the Diocese of Illyricum, was a diocese of the Late Roman Empire. The seat of the vicarius (governor of the diocese) was Sirmium. History It was originally part of the praetorian prefecture of Italy and was incorporated by the praetorian prefecture of Illyricum when it was established in 347. Disputed by the two halves of the Empire in the following years, the Diocese of Pannonia was one of the two dioceses in the eastern quarters of the Tetrarchy not belonging to the cultural Greek half of the empire (the other was Dacia), and so it was transferred back to the Western Empire at the death of Theodosius I in 395 and was joined to the Prefecture of Italy as the Diocese of Illyricum. In 425 Galla Placidia gave the diocese of Illyricum to Eastern Emperor Theodosius II. Its ultimate fate is uncertain. Pannonia was lost to the Huns in the 440s, although Dalmatia was retained by the Western Empire until c. 480. The Ostrogoth king of Italy Theodoric the Great conquered Pannonia in the late 5th century, possibly reestablishing the diocese. Structure The Diocese of Pannonia (Diocese of Illyricum occidentalis) included the Roman provinces of Pannonia Prima, Pannonia Valeria, Pannonia Savia, Pannonia Secunda, Noricum Mediterraneum, Noricum Ripensis and Dalmatia. Also under its jurisdiction were the Exarch of Sirmium, the Metropolis of Lauriacum, Vindomana, Sirmium, Salona, Salisburgium and the "locus incertus" (the "unknown location", see: Miholjanec). List of known Vicars Valerius Licinius (308-314). Later usage of the term In the 9th century, Diocese of Pannonia was also a name of the ecclesiastical territory of the Christian church whose archbishop was Saint Methodius. See also Pannonia Praetorian prefecture of Illyricum Illyricum (Roman province) References Literature External links Illyricum Map Pannonia Pannonia Praetorian prefecture of Illyricum Praetorian prefecture of Italy Illyricum (Roman province) Austria in the Roman era Bosnia and Herzegovina in the Roman era Croatia in the Roman era Dalmatia (Roman province) Hungary in the Roman era Serbia in the Roman era Slovenia in the Roman era Ancient history of Vojvodina History of Syrmia Historical regions of Bosnia and Herzegovina Historical regions in Slovenia 314 establishments States and territories established in the 310s 4th-century establishments in the Roman Empire 440s disestablishments 5th-century disestablishments in the Roman Empire