The Histories of Alexander the Great (Latin: Historia Alexandri Magni Libri) is an account of Alexander's conquests in ten books, of which only eight survive. The surviving part begins with book three, which describes the Macedonian army's passage through Phrygia and the famous episode of the cutting of the Gordian knot.
Little is known for certain about the author, Quintus Curtius Rufus, who is generally thought to have lived in the first century CE. The work's dramatic but uncritical tone has suggested to some that is was conceived to serve a Roman imperial propaganda purpose.
Free online texts
Internet Archive: History of Alexander, Latin text and English translation by John C. Rolfe. Volume 1 | Volume 2. Multiple formats. Loeb edition, although facing pages do not correspond to one another in this scan.
Internet Archive: Historia Alexandri Magni Libri Qui Supersunt. Latin text, Teubner edition (1908). Multiple formats.
Latin Library: Historia Alexandri Magni Libri Qui Supersunt. Latin text. HTML format.
PHI Latin texts: Historiae Alexandri Magni. Latin text. HTML format.
Wikisource: Historia Alexandri Magni regis Macedonum. Latin text. HTML and other formats.
Livius: Quintus Curtius Rufus
The Great Conversation: Further reading at Tom's Learning Notes
David Hume: An Enquiry Concerning Human Understanding - "The veracity of Quintus Curtius is as much to be suspected when he describes the supernatural courage of Alexander, by which he was hurried on singly to attack multitudes, as when he describes his supernatural force and activity, by which he was able to resist them. So readily and universally do we acknowledge a uniformity in human motives and actions as well as in the operations of body. "