The Royal Library of Alexandria, or Ancient Library of Alexandria, in Alexandria, Egypt, was a large and significant great library of the ancient world. Named after Alexander the Great, it flourished under the patronage of the Ptolemaic dynasty and functioned as a major center of scholarship from its construction in the third century B.C. until its destruction in 48 B.C. around the time of Rome's conquest of Egypt. Alexander, although picking the site and planning the general layout of the city, died before he could take part in the construction of the library or academy that was created in his name.

The Greek term bibliotheke (βιβλιοθήκη), used by many historians of the era, refers to the [royal] "Collection of Books", not to any building, nor to the social networks which sustained and operated the collection, which complicates tracking the history and chronology of its destruction. The Royal Collection can be viewed as having begun in the Royal Quarter's building(s), commonly known as "The Great Library," and continued to be housed, at least in part, at the Serapeum "Daughter Library" (Abaddi)

Generally thought to have been founded at the beginning of the third century BC, the library was conceived and opened either during the reign of Ptolemy I Soter or during the reign of his son Ptolemy II. Plutarch (AD 46–120) wrote that during his visit to Alexandria in 48 BC, Julius Caesar might have accidentally burned the library when he set fire to his own ships to frustrate Achillas' attempt to limit his ability to communicate by sea. According to Plutarch's account, this fire spread to the docks and then to the library.

However, this version of events is not confirmed in contemporary accounts of Caesar's visit. In fact, it has been reasonably established that segments of its collection were partially destroyed on several occasions before and after the first century BC. A modern conflation (no older than the late eighteenth century) attributes the destruction to Coptic Christian Archbishop Theophilus of Alexandria in 391, who called for the destruction of the Serapeum -- the Daughter library and a temple to the god Serapis.

Intended both as a commemoration and an emulation of the original, the Bibliotheca Alexandrina was inaugurated in 2002 near the site of the old library.