Dio Cassius of Nicaea (Δίων ὁ Κάσσιος ὁ Κοκκηϊανός) Life Dio Cassius (c. 164–c. 229 CE), a Roman senator and historian of Greek origin from Nicaea in Bithynia, pursued a successful political career, achieving the consulship twice [1][2]. His career spanned the reigns of Commodus through Severus Alexander, during which he served as a provincial governor. He dedicated over two decades to researching, writing, and revising his monumental history before retiring to Nicaea [1].

Works His principal work is the 80-book Roman History (Ῥωμαϊκὴ Ἱστορία), covering Rome from its origins to 229 CE [1][2]. Substantial portions survive for Books 36–60, while the rest is known through later epitomes by John Xiphilinus and John Zonaras [1][2]. He also authored an earlier work on the dreams portending Septimius Severus's rise [1].

Significance Dio Cassius provides a crucial insider’s perspective on imperial politics and senatorial procedure [1][2]. His analytical history, written in Atticizing Greek, explains events through constitutional change and the decline of republican institutions, forming a vital source for the late Republic and early Empire [1].

Sources 1. Stanford Encyclopedia of Philosophy: Cassius Dio: https://plato.stanford.edu/entries/dio-cassius/ 2. Encyclopædia Britannica: Cassius Dio: https://www.britannica.com/biography/Dio-Cassius 3. Oxford Research Encyclopedia of Classics: Cassius Dio: https://oxfordre.com/classics/view/10.1093/acrefore/9780199381135.001.0001/acrefore-9780199381135-e-1360