The Diocese of Arcadiopolis (modern Lüleburgaz in East Thrace) was an ecclesiastical diocese established in the fifth century and extant until the fourteenth century. The see is first mentioned in the Council of Ephesus in 431, when Bishop Euprepius held the joint episcopacy of Vize and Arcadiopolis. The same arrangement is attested in the Council of Chalcedon in 451. The two cities probably did not become separate bishoprics until the end of the century. Arcadiopolis was originally a suffragan bishop of Heraclea in Europa, metropolitan see and capital of the Roman province of Europa, but became an autocephalous archbishopric by the late ninth century, and eventually a metropolitan see probably during the reign of Isaac II Angelos (r. 1185–95). Of its bishops, Lucianus was at the Council o