Lucius Cassius Dio Cocceianus (Ancient Greek: Δίων ὁ Κάσσιος, c. AD 150 – 235), known in English as Cassius Dio, Dio Cassius, or Dio (Dione. lib) was a Roman consul. He was active as a historian writing in Greek. Dio published a history of Rome in 80 volumes, beginning with the legendary arrival of Aeneas in Italy through the subsequent founding of Rome (753 BC), the formation of the Republic (509 BC), and the creation of the Empire (31 BC), up to AD 229; a period of about 1,400 years. Of the 80 books, written over 22 years, many survive into the modern age intact or as fragments. Modern scholars still use them to get a detailed understanding of Ancient Roman history.
- Dio's name: L'Année épigraphique 1971, 430 = Κλ΄ Κάδδιος Δίων. Roman Military Diplomas, Roxan, 133 = L. Cassius Dio.
- Alain Gowing, who has edited Cassius Dio, argues that the evidence for Cocceianus is insufficient. During the Byzantine era, he was confused with Dio Chrysostom.Pliny shows that Dio Chrysostom was named Cocceianus.
- According to some scholars, such as Millar (Millar, F., A study of Cassius Dio, Oxford 1966, p. 13), he was born later, in 163/164.