Roman History, Volume I

Dio Cassius (Cassius Dio), circa 150–235 CE, was born at Nicaea in Bithynia in Asia Minor. Upon the death of his father, who was the Roman governor of Cilicia, he went to Rome in 180, entered the Senate, and served as an advocate under Emperor Commodus. During his career, he held high offices and became a close friend of several emperors. His roles included governor of Pergamum and Smyrna, consul in 220, proconsul of Africa, governor of Dalmatia and later Pannonia, and consul once more in 229.

Of the eighty books of Dio's great work Roman History, which spans from the legendary landing of Aeneas in Italy to the reign of Alexander Severus (222–235 CE), we currently possess Books 36–60. These books, covering the years 68 BCE–47 CE, have gaps in sections 36 and 55–60. The missing portions are partly supplied by the writings of Zonaras, who relies closely on Dio, and for some of the later gaps (from Book 35 onwards) by John Xiphilinus (of the eleventh century). Additionally, there are numerous excerpts available. The research opportunities afforded by Dio's official duties, combined with his diligence, render him a significant source for the history of Rome during the last years of the republic and the first four emperors.

The Loeb Classical Library edition of Dio Cassius's works is presented in nine volumes.