The Royal Library of Alexandria, or Ancient Library of Alexandria, in Alexandria, Egypt, was one of the largest and most significant libraries of the ancient world. It flourished under the patronage of the Ptolemaic dynasty and functioned as a major center of scholarship from its construction in the 3rd century BC until the Roman conquest of Egypt in 30 BC. With collections of works, lecture halls, meeting rooms, and gardens, the library was part of a larger research institution called the Musaeum of Alexandria, where many of the most famous thinkers of the ancient world studied.
The library was conceived and opened either during the reign of Ptolemy I Soter (323-283 BC) or during the reign of his son Ptolemy II (283-246 BC). As a symbol of the wealth and power of Egypt, it employed many scribes to borrow books from around the known world, copy them, and return them. Most of the books were kept as papyrus scrolls, and though it is unknown how many such scrolls were housed at any given time, their combined value was incalculable.
The library is famous for having been burned, resulting in the loss of many scrolls and books, and has become a symbol of the destruction of cultural knowledge. Ancient sources differ widely on who is responsible for the destruction and when it occurred. Although there is a mythology of the burning of the Library at Alexandria, the library may have suffered several fires or acts of destruction over many years. Possible occasions for the partial or complete destruction of the Library of Alexandria include a fire set by Julius Caesar in 48 BC, an attack by Aurelian in the 270s AD, the decree of Coptic Pope Theophilus in 391, and the Muslim conquest of Egypt in 642. After the main library was fully destroyed, ancient scholars used a "daughter library" in a temple known as the Serapeum, located in another part of the city. According to Socrates of Constantinople, Coptic Pope Theophilus destroyed the Serapeum in 391 AD.