Cassius Dio Cocceianus
c160 - c229 AD
Although the proper Roman order of his name is as given above he is more commonly known under the Greek order of his name as Dio Cassius, which is generally the convention that is followed today.
He was a native of Bithynia
and the date of his birth has been placed between 155 and 164 A.D. His father was Cassius Apronianus, a Roman senator, who served as governor of Cilicia
and of Dalmatia
In the year 180 Dio was a senator in Rome and therefore a contemporary witness of the events that saw the overthrow of the emperor Commodus as well as his successors Pertinax and his Didius Julianus and the accession to power of Septimius Severus.
Dio served as a consul under Septimius Severus and wrote a small book detailing the various dreams and portents that informed Septimius Severus of his future greatness. He then seems to have withdrawn from public affairs and retired to Capua where he spent his time gathering material and writing a considerable part of his history.
He returned to public life under the reign of Caracalla and under the emperor Alexander Severus became the proconsul of Africa and served as governor successively of Dalmatia and Upper Pannonia. In 229 he became consul for the second time before retiring to Nicaea, his native city and very probable died soon afterwards.
He best known for his Roman History, a work in some eighty books that begins with the origins of Rome and ends with the overthrow of Elagabalus and his replacement by Alexander Severus a period of nearly a thousand years. About one third of Dio's History has survived intact, most of the remainder is known to us through both excerpts contained in various Byzantine collections and the Epitomes of the work produced by Zonaras and Xiphilinus.
For more detail see http://www.ukans.edu/history/index/europe/ancient_rome/E/Roman/Texts/Cassius_Dio/Introduction*.html. A translation of the Roman History is available at www.ku.edu/history/index/europe/ancient_rome/E/Roman/Texts/ Cassius_Dio/home.html