Sirmium (today Sremska Mitrovica) was ancient city in Roman Pannonia. Present day region of Srem was named after this city. Sirmium originally was Illyrian town conquered by Romans in the 1st century BC. Town was very important in Roman Empire. It was main city of Roman Pannonia and one of four capital cities of Roman Empire. Six Roman Emperors were born in this city or in its surroundings:

• Decius Traian (249-251)
• Aurelian (270-275)
• Probus (276-282)
• Maximianus Herculius (285-310)
• Constantius II (337-361)
• Gratian (367-383)

See also

• Sremska Mitrovica
• Council of Sirmium