Aenus (gr . Ainos) was a city in Thrace, a Greek colony.

Aenus was an ancient city on the southeastern coast of Thrace. Formerly called Poltyobria (or Poltymbria), it was located near the mouth of the Hebrus River, not far from the Melas Gulf (modern Gulf of Saros), which is formed by the Thracian Chersonesus to the east. The city was said to be founded (or at least settled) by migrants from Lesbos.

Aenus is mentioned by several ancient authors (e.g., Homer, Strabo, Apollodorus), and makes several appearances in Greek mythology. Its mythical and eponymous founder was said to be Aeneus, a son of the god Apollo and father of Cyzicus and Aenete. Another mythical ruler, named Poltys, son of Poseidon, entertained Heracles when he came to Aenus. On that occasion, Heracles (during his ninth labor , to take the belt of the Amazon queen Hippolyte) slew Poltys' insolent brother Sarpedon on the beach of Aenus. According to Strabo, Sarpedon is the name of a geographical feature nearby Aenus, so both Poltys and Sarpedon would appear to be eponyms.

Ainos

In the Iliad, Homer mentions that the leaders of Troy's Thracian allies, Acamas and Peiros, came from Aenus

Little especial mention of Aenus occurs till a comparatively late period of Greek history. It is mentioned by Thucydides (I. c.) that Aenus sent forces to the Sicilian expedition as a subject ally of Athens. At a later period we find it successively in the possession of Ptolemy Philopator, 222 BC (Pol. v. 34), of Philip, king of Macedonia, 200 BC 200 (Liv. xxxi. 16), and of Antiochus the Great.

After the defeat of the latter by the Romans, Aenus was declared free. (Liv. xxxviii. 60.) It was still a free city hi the time of Pliny (iv. 11).

Athenaeus (p. 351) speaks of the climate of Aenus as being peculiarly ungenial. He describes the year there as consisting of eight months of cold, and four of winter.