He was a senator under Commodus and governor of Smyrna following the death of Septimius Severus; he became a suffect consul in approximately the year 205.

[10] Dio published a Roman History (Ῥωμαϊκὴ Ἱστορία, Rhōmaïkḕ Historía) in 80 books in Greek, later translated into Latin as the Historia Romana.

[11][12] The books cover a period of approximately 1,400 years, beginning with the tales from Roman mythology of the arrival of the legendary Aeneas in Italy (c. 1200 BC) and the founding of Rome by his descendant Romulus (753 BC); as well as the historic events of the republican and imperial eras through 229 AD.

The work is one of only three written Roman sources that document the British revolt of 60–61 AD led by Boudica.

[16][17][18] The first 21 books have been partially reconstructed based on fragments from other works, as well as the 12th-century epitome of Joannes Zonaras who used Dio's Roman History as a main source.

Of the 20 subsequent books in the series, there remain only fragments and the meager abridgement of John Xiphilinus, a Byzantine monk from the 11th century sponsored by emperor Michael VII Doukas.