Diodorus Siculus or Diodorus of Sicily was an ancient Greek historian. He is known for writing the monumental universal history Bibliotheca historica, in forty books, fifteen of which survive intact, between 60 and 30 BC. The history is arranged in three parts. The first covers mythic history up to the destruction of Troy, arranged geographically, describing regions around the world from Egypt, India and Arabia to Europe. The second covers the time from the Trojan War to the death of Alexander the Great. The third covers the period to about 60 BC. Bibliotheca, meaning 'library', acknowledges that he was drawing on the work of many other authors.

Bibliotheca historica is a work of universal history by Diodorus Siculus. It consisted of forty books, which were divided into three sections. The first six books are geographical in theme, and describe the history and culture of Egypt, of Mesopotamia, India, Scythia, and Arabia (II), of North Africa (III), and of Greece and Europe (IV–VI). In the next section, he recounts human history starting with the Trojan War, down to the death of Alexander the Great. The last section concern the historical events from the successors of Alexander down to either 60 BC or the beginning of Caesar's Gallic War in 59 BC. He selected the name "Bibliotheca" in acknowledgement that he was assembling a composite work from many sources. Of the authors he drew from, some 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.