|Diocese of Pannonia|
|Diocese of the Roman Empire|
|Historical era||Late Antiquity|
• conquest by the Huns
The Diocese of Pannonia (Latin: Dioecesis Pannoniarum, 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.
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.
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 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.