Diodorus Siculus (Greek: ), was a Greek historian who flourished in the 1st century BC. According to Diodorus own work, he was born at Agyrium in Sicily (now called Agira). With but one exception, antiquity affords no further information about Diodorus’ life and doing, than is to be found in his own work, Bibliotheca historica. Only Jerome, in his Chronicon under the year of Abraham 1968 (49 BC) writes "Diodorus of Sicily, a writer of Greek history, became illustrious". His English translator, Charles Henry Oldfather, remarks on the "striking coincidence" that one of only two known Greek inscriptions from Agyrium (I.G. XIV, 588) is the tombstone of one "Diodorus, the son of Apollonius".
Diodorus' universal history, which he named Bibliotheca historica ("Historical Library"), consisted of forty books, of which 1–5 and 11–20 survive, and were divided into three sections. The first six books treat the mythic history of the non-Hellenic and Hellenic tribes to the destruction of Troy and are geographical in theme, and describe the history and culture of Ancient Egypt (book I), of Mesopotamia, India, Scythia, and Arabia (II), of North Africa (III), and of Greece and Europe (IV - VI). In the next section (books VII - XVII), he recounts the history of the World starting with the Trojan War, down to the death of Alexander the Great. The last section (books XVII to the end) concerns the historical events from the successors of Alexander down to either 60 BC or the beginning of Caesar's Gallic War. (The end has been lost, so it is unclear whether Diodorus reached the beginning of the Gallic War as he promised at the beginning of his work or, as evidence suggests, old and tired from his labors he stopped short at 60 BC.) He selected the name "Bibliotheca" in acknowledgement that he was assembling a composite work from many sources. The authors he drew from, who have been identified, include: Hecataeus of Abdera, Ctesias of Cnidus, Ephorus, Theopompus, Hieronymus of Cardia, Duris of Samos, Diyllus, Philistus, Timaeus, Polybius and Posidonius.