Catholic Encyclopedia (1913)/Diocese of Sirmium
Sirmium, situated near the modern town of Mitrovitz in Slavonia; its church is said to have been founded by St. Peter. The district of Szerém was subject to the Archbishop of Kalocsa after the Christianization of Hungary. In 1228, the archbishop petitioned the Holy See, in consideration of the large extent of his diocese, to found a new bishopric, and in 1229 Gregory IX established the See of Szerém, the jurisdiction of which covered almost exclusively the country on the right bank of the Sava River. The see was under the Turkish Government in 1526. It had no bishop from 1537 to 1578, and was held by a titular bishop after 1624. In 1709 the see was re-established with some changes in its territory. Clement XIV united it with Bosnia and Diakovár in 1773.
SZÖRÉNYI, Vindiciœ Sirmienses (Buda, 1746); FARLATI, Illyricum sacrum, VII, 449-811; PRAY, Specimen Hierarchiaœ Hungariœ, II, 362-95; A katolikus Magyarország (Budapest, 1902).