DIO CASSIUS (more correctly CASSIUS DIO) COC CEIANUS (c. A.D. Roman historian, born at Nicaea in Bithynia. His father was Cassius Apronianus, governor of Dal matia and Cilicia under Marcus Aurelius, and on his mother's side he was the grandson of Dio Chrysostom. After his father's death Dio Cassius went to Rome (180) and became a member of the senate. During the reign of Commodus, Dio practised as an advo cate and held the offices of aedile and quaester. He was raised to the praetorship by Pertinax (193) but did not assume office till the reign of Septimius Severus, with whom he was for a long time on intimate terms. By Macrinus he was entrusted with the adminis tration of Pergamum and Smyrna, and on his return to Rome he was made consul (c. 22o). After this he obtained the proconsul ship of Africa, and again on his return was sent as legate succes sively to Dalmatia and Pannonia. He was granted a second con sulship by Alexander Severus, in 2 29, but soon afterwards retired to Nicaea, where he died. Before writing his history of Rome (Romaika), Dio Cassius had dedicated to Severus an account of various prodigies which had presaged his elevation to the throne (perhaps the 'Evo&ca attributed to Dio by Suidas), and had also written a biography of his fellow-countryman Arrian. The history of Rome, which is written in Greek, consisted of 8o books, begin ning with the landing of Aeneas in Italy and ending with the reign of Alexander Severus (2 2 2-23 5) . We possess books 3 6-6o (68 B.C.—A.D. 4 7) ; books 36 and 55-6o are imperfect. We also have part of 35 and 36-8o in the epitome of John Xiphilinus, an IIth century Byzantine monk. For the earlier period the loss of Dio's work is partly supplied by the history of Zonaras, who followed him closely. Numerous fragments are also contained in the ex cerpts of Constantine Porphyrogenitus. Dio's work is a most im portant authority for the history of the last years of the republic and the early empire. His industry was great and the various offices he held gave him opportunities for historical investigation. His narrative shows the hand of the practised soldier and poli tician ; the language is correct and free from affectation. But his work, although far more than a mere compilation, is not remarkable for impartiality, vigour of judgment, or critical historical faculty.
The best edition with notes is that of H. S. Reimar (1750-52) , new ed. by F. G. Sturz (1824-36) ; text by I. Melber (1890 foll.), with account of previous editions, and U. P. Boissevain (1895-1926) ; translations by H. B. Foster (Troy, New York, 19o5 foil.), with full bibliography, and E. Cary (Loeb series, 1912) ; see also W. Christ, Geschichte der Griechischen Literatur (1898), p. 675; E. Schwartz in Pauly-Wissowa's Realencyklopldie, iii. pt. 2 (1899) ; C. Wachsmuth, Einleitung in das Studium der alten Geschichte (1895).