The Alexander Romance is an account of the life and exploits of Alexander the Great. Of uncertain authorship, it has been described as "antiquity's most successful novel". The Romance describes Alexander the Great from his birth, to his succession of the throne of Macedon, his conquests including that of the Persian Empire, and finally his death. Although constructed around a historical core, the romance is mostly fantastical, including many miraculous tales and encounters with mythical creatures such as sirens or centaurs. In this context, the term Romance refers not to the meaning of the word in modern times but in the Old French sense of a novel or roman, a "lengthy prose narrative of a complex and fictional character" (although Alexander's historicity did not deter ancient authors from using this term).

It was widely copied and translated, accruing various legends and fantastical elements at different stages. The original version was composed in Ancient Greek some time before 338 AD, when a Latin translation was made, although the exact date is unknown. Some manuscripts pseudonymously attribute the text's authorship to Alexander's court historian Callisthenes, and so the author is commonly called Pseudo-Callisthenes.

In premodern times, the Alexander Romance underwent more than 100 translations, elaborations, and derivations in dozens of languages, including almost all European vernaculars as well as in every language from the Islamicized regions of Asia and Africa, from Mali to Malaysia. Some of the more notable translations were made into Coptic, Ge'ez, Middle Persian, Byzantine Greek, Arabic, Persian, Armenian, Syriac, and Hebrew. Owing to the great variety of distinct works derived from the original Greek romance, the "Alexander romance" is sometimes treated as a literary genre, instead of a single work.

Nectanebo II, the last Pharaoh of Egypt, foresees that his kingdom will fall to the Persians and so flees to the Macedonian court under the guise of the identity of a magician. In his time there, he falls in love with the wife of king Philip II of Macedon, Olympias. Olympias becomes pregnant by Nectanebo, but his paternity is kept a secret. Philip develops a suspicion of an affair between the two, but Nectanebo allays Philip's suspicions by sending a magic sea-hawk to him in a dream. Alexander is born from this pregnancy, but while he is growing up he kills Nectanebo, who reveals Alexander's paternity as he dies. Alexander begins to be educated by Aristotle and competes in the Olympics.

After Philip dies, Alexander begins his campaigns into Asia, although the story is unclear with respect to the order and location of the campaigns. Once he reaches Egypt, an oracle of the god Amun instructs him where to go to create the city that will become Alexandria. The march into Asia continues and Alexander conquers Tyre. He begins exchanging letters with the Persian emperor Darius III, though the story now delves into more campaigns in Greece. The Persian march resumes and eventually Alexander conquers the Persians. He marries Roxane, the daughter of Darius, and writes letters to Olympias describing all he saw and his adventures during his conquests, including his wandering through the Land of Darkness, search for the Water of Life, and more.

Next, he proceeds to conquer India from which he writes letters to Aristotle, though he also receives an omen about his coming death in this time. He visits the temples of the sun and moon, and makes the Amazons his subjects. During his return, as he reaches Babylonia, he meets the son of Antipater (the figure ruling Macedonia in Alexander's stead during the journeys of the latter) who was sent to poison Alexander. The conspiracy succeeds, and Alexander begins to die, though he names the rulers who will control the provinces of his empire after he is gone before ultimately succumbing to the poison. Ptolemy I Soter receives his body in the Egyptian city of Memphis where the priests order it to be sent to Alexandria, the greatest city he had built during his march. The work concludes by providing a list of all the cities that Alexander founded.

The Romance locates the Gates of Alexander between two mountains called the "Breasts of the North" (Greek: Μαζοί Βορρά). The mountains are initially 18 feet apart and the pass is rather wide, but Alexander's prayers to God causes the mountains to draw nearer, thus narrowing the pass. There he builds the Caspian Gates out of bronze, coating them with fast-sticking oil. The gates enclosed twenty-two nations and their monarchs, including Gog and Magog (therein called "Goth and Magoth"). The geographic location of these mountains is rather vague, described as a 50-day march away northwards after Alexander put to flight his Belsyrian enemies (the Bebrykes, of Bithynia in modern-day North Turkey).

In the α recension of the Alexander Romance, Alexander's father is an Egyptian priest named Nectanebo who sports a set of ram horns. After his death, Alexander is described as "the horned king" (βασιλέα κερασφόρον) by an oracle instructing Ptolemy, a general of Alexander, on where to bury him. This statement was repeated in the Armenian recension of the Alexander Romance in the 5th century. The use of the horned motif, representing the horns of Zeus Ammon to visualize Alexander stems from much earlier, originally in coinage depicting Alexander by his immediate successors Ptolemy I Soter of Egypt and more prominently the king of Thrace Lysimachus were the earliest produce coinage of Alexander with the rams horns. The motif would be carried over into later Alexander legends, such as the Armenian translation of α and the Syriac Alexander Legend.