Agatharchides of Cnidus was a Greek historian and geographer of the Hellenistic period, active in Alexandria during the reigns of Ptolemy VI Philometor and Ptolemy VIII Euergetes II [1]. Described as a Peripatetic, he served as a tutor and spent his career within the Ptolemaic court, where he accessed official archives [1][2]. He likely retired to write following political upheaval under Ptolemy VIII [2].

His major works survive only in fragments preserved by authors like Photius, Diodorus Siculus, and Strabo [1][2][3]. These include Τὰ κατὰ τὴν Ἀσίαν (Events in Asia) in ten books, Τὰ κατὰ τὴν Εὐρώπην (Events in Europe) in forty-nine books, and the significant geographical treatise Περὶ τῆς Ἐρυθρᾶς θαλάσσης (On the Erythraean Sea) in five books [1][2][3].

Agatharchides is a crucial source for the geography and ethnography of the Hellenistic world, particularly for the Red Sea region, Arabia, and Northeast Africa. His critical methodology and vivid narrative, especially evident in On the Erythraean Sea, made him an important authority for later geographers and historians [1][2][3].

Sources 1. Oxford Research Encyclopedia of Classics: Agatharchides: https://oxfordre.com/classics/view/10.1093/acrefore/9780199381135.001.0001/acrefore-9780199381135-e-191 2. Encyclopædia Britannica: Agatharchides of Cnidus: https://www.britannica.com/biography/Agatharchides-of-Cnidus 3. Perseus Digital Library: Entry for Agatharchides in Smith's Dictionary of Greek and Roman Biography and Mythology: http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0104%3Aentry%3Dagatharchides-bio-1