was a Roman senator and had been governor of Dalmatia and Cilicia; to
the latter post Dio bore his father company (Books 49, 36; 69, 1; 72,
7). The date of the historian's birth is determined approximately as
somewhere from 150 to 162 A.D., that is, during the last part of the
reign of Antoninus Pius or at the beginning of the reign of Marcus
Aurelius. The town where he first saw the light was Nicæa in Bithynia.

The careful education which the youth must have had is evident, of
course, in his work. After the trip to Cilicia already referred to Dio
came to Rome, probably not for the first time, arriving there early in
the reign of Commodus (Book 72, 4). This monster was overthrown in 192
A.D.; before his death Dio was a senator (Book 72, 16): in other
words, he was by that time above the minimum age, twenty-five years,
required for admission to full senatorial standing; and thus we gain
some scanty light respecting the date of his birth. Under Commodus he
had held no higher offices than those of quæstor and ædile: Pertinax
now, in the year 193, made him prætor (Book 73, 12). Directly came the
death of Pertinax, as likewise of his successor Julianus, and the
accession of him whom Dio proudly hailed as the "Second
Augustus,"--Septimius Severus. The new emperor exerted a great
influence upon Dio's political views. He pretended that the gods had
brought him forward, as they had Augustus, especially for his work.
The proofs of Heaven's graciousness to this latest sovereign were
probably by him delivered to Dio, who undertook to compile them into a
little book and appears to have believed them all; Severus, indeed,
had been remarkably successful at the outset. Before long Dio had
begun his great work, which he doubtless intended to bring to a
triumphant conclusion amid the golden years of the new prince of
peace.