Agatharchides of Cnidus, ( Αγαθαρχίδης) was a Greek historian and geographer (flourished 2nd century BC); Strabo (14.2.15) describes him as a Peripatetic. He is known as the author of a number of works, which only survive in quotation.

As Stanley M. Burstein notes, the "evidence for Agatharchides' life is meagre." Photius, describes him as a threptos, a kind of assistant of servile origin, to Cineas and states that he was later a secretary to Heraclides Lembrus. Cineas served as a councillor to Ptolemy VI; Heraclides is best known for negotiating the treaty that ended Antiochus IV's invasion of Egypt in 169 BC.

Agatharchides furnishes few clues about his own life. At the conclusion of his On the Erythraean Sea, he apologizes for being unable to complete his work "since our age is unable to similarly bear the toil" and "as a result of the disturbances in Egypt" he no could longer access the official records (a fragment cited by Photius in his Bibliotheca Cod. 250.110, 460b). There are two possible occasions when this could have happened: the first was in 145 BC, when Ptolemy VIII purged Alexandria of the intellectuals who supported his rivals for the throne; and in 132 BC after Ptolemy, who had been driven from his kingdom by a rebellion in Alexandria, returned and exacted reprisals on thatcity. While most scholars have favored the later date, Burstein argues for the earlier one.

Extracts from the first book of his Erythraean Sea, written in the first person and advocating a military campaign into the lands south of Egypt, led early scholars to deduce that Agatharchides was an important political figure of his time, and served as a guardian to the young Ptolemy IX, an interpretation still repeated in some accounts like the Oxford Classical Dictionary article on Agatharchides. However, at least as early as 1810, when B.G. Nielbuhr pointed out that these excerpts were from a speech, and not part of the narrative of his book, this theory has been recognized as conflicting with other known historical facts.

Agatharchides' was not well known in ancient times. Of his two major works, Affairs in Asia ("Ta kata ten Asian") in 10 books, and Affairs in Europe ("Ta kata ten Europen") in 49 books, only a few fragments survive, too few to provide us with any sense of the contents of either. However, for his On the Erythraean Sea ("Peri ten Erythras thalasses") in five books, almost the entire fifth book, a geographical treatise on the Horn of Africa and the lands around the Red Sea, has survived almost intact. According to Burstein, "the comparative soberness of Agatharchides' treatment compared to previous accounts and the wealth of information contained in it led to a quick recognition . . . [that it was] a valuable summary of the results of Ptolemaic exploration." Among other things, On the Erythraean Sea contains a detailed account of Ptolemaic gold mining techniques. Material from this book is quoted directly or indirectly by Diodorus Siculus, Strabo, Pliny the Elder, Aelian and other authors. Although his work was superceded by more detailed accounts in the 2nd century AD, Photius found a copy of Erythraean Sea in the tenth century, from which he preserved extensive extracts in his Bibliotheca.

Agatharchides moon crater
48 km diameter
19.8S – 30.9W

Bibliography

Stanley M. Burstein, translator and editor. Works Issued by the Hakluyt Society: Agatharchides of Cnidus, On the Erythraean Sea. Second series, no. 172. London: Hackluyt Society, 1989.

H Verdin, "Agatharchide de Cnide et les fictions des poètes" Purposes of history: studies in Greek historiography from the 4th to the 2nd centuries B.C.: proceedings of the international colloquium, Leuven, 24-26 May 1988. Studia Hellenistica 30 (Lovanii 1990) p. 1-15. PA25 .S8 no.30