Bibliotheca Historica (Latin; Greek: Βιβλιοθήκη Ἱστορική, Bibliothḗkē Historikḗ), also known as the Historical Library or Library of History, 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 (Book I), of Mesopotamia, India, Scythia, and Arabia (II), of North Africa (III), and of Greece and Europe (IV–VI). In the next ten books, he recounts human history starting with the Trojan War (Book VII) down to the death of Alexander the Great (XVII). The final section concerns the historical events from the successors of Alexander (Book XVIII) down to the time of the First Triumvirate of the late Roman Republic (XL). The end of the work has been lost, and it is unclear whether Diodorus actually reached the beginning of Caesar's Gallic War in 59 BC (as he promises at the beginning of the work) or, as evidence suggests, he stopped short at 60 BC owing to old age and weariness from his labors. He selected the name "Library" as an acknowledgement that he was assembling a composite work drawing from many sources. Of the authors he used, 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.
Diodorus's immense work has not survived intact. Only Books I–V and Books XI–XX remain in their entirety. The rest exists only in fragments preserved in Photius and in the Excerpta of Constantine Porphyrogenitus.