Dio Cassius (Cassius Dio Cocceianus) (dīo kăsh´əs), c.155–235?, Roman historian and administrator, b. Nicaea in Bithynia. He was a grandson of Dio Chrysostom. His rise in civil and military office was steady; he became a senator (c.180), praetor (193), consul (220?), proconsul in Africa (224), legate in Dalmatia (226), legate in Pannonia (227), and consul again (229). He was a good commander, but he remained in favor more for his literary works than for his abilities in office. His great work, partially extant, was a history of Rome (written in Greek) from the earliest times until Dio Cassius' own period. Of the original 80 books, 19 survive in full. They are a reputable source for the period of the later republic and the first two centuries AD Dio Cassius tried earnestly to study all available sources in the light of a moderate skepticism.