Carnuntum was the largest Roman military camp and provincial centre on the Middle Danube, in the province of Pannonia Superior (Upper Pannonia). Founded at the beginning of the 1st century CE as the winter camp of Legio XV Apollinaris, by the 2nd century it had become a fortified city with an amphitheatre, baths, and a forum. It was the most important base of the Roman army for the control of Dacia and Germania. The population in the Antonine period is estimated at 50,000 — the largest Romanised centre north of the Alps.

During the Marcomannic Wars (166–180 CE), Carnuntum became Marcus Aurelius's main headquarters on the Danube front. The emperor spent a significant part of the campaign of 171–173 there, against the Marcomanni, Quadi, and Sarmatians — the gravest military crisis of the later High Principate.

• A. Birley, Marcus Aurelius: A Biography, rev. ed., Routledge 2000, especially ch. 7 (the Marcomannic Wars)
• W. Jobst (ed.), Carnuntum Jahrbuch (the Austrian Archaeological Institute series, 1989–present)
• M. Kandler, Carnuntum, in the Roman Limes series
• F. Beck & Y. Burnaud, Carnuntum: Antike Hauptstadt vor den Toren Wiens, Phoibos Verlag, 2006
• Historia Augusta, Vita Marci (late and not entirely reliable, but the only biographical source that survives)