Cardia (in Greek Kαρδία), anciently the chief town of the Thracian Chersonese (today Gallipoli peninsula), was situated at the head of the gulf of Melas (today Saros bay). It was originally a colony of the Milesians and Clazomenians; but subsequently, in the time of Miltiades (late 6th century BC), the place also received Athenian colonists, as proved by Miltiades tyranny (515–493 BC). But this didn't make Cardia necessarily always pro-Athenian: when in 357 BC Athens took control of the Chersonese, the latter, under the rule of a Thracian prince, was the only city to remain neutral; but the decisive year was 352 BC when the city concluded a treaty of amity with king Philip II of Macedonia. A great crisis exploded when Diopeithes, an Athenian mercenary captain, had in 343 BC brought Attic settlers to the town; and since Cardia was unwilling to receive them, Philip immediately sent help to the town. The king proposed to settle the dispute between the two cities by arbitration, but Athens refused. The town was destroyed by Lysimachus about 309 BC, and although it was afterwards rebuilt, it never again rose to any degree of prosperity, as Lysimachia, which was built in its vicinity and peopled with the inhabitants of Cardia, became the chief town in that neighbourhood. Cardia was the birthplace of Alexander's secretary Eumenes and of the historian Hieronymus.
- Curtius, Ernst; The history of Greece, Adolphus William Ward (translator); New York, (1874)
- Smith, William (editor); Dictionary of Greek and Roman Geography, "Cardia", London, (1854)
- Herodotus, Histories, vii. 58, vi. 34, ix. 115; Demosthenes, Speeches, "On the Chersonese", 58, 64, "On the Halonnesus", 41, 43, 44
- Pausanias, Description of Greece, i. 9
- Strabo, Geography, vii. 7; Pausanias, i. 10; Appian, The Civil Wars, iv. 88; Ptolemy, Geographia, iii. 12; Stephanus of Byzantium, Ethnica, s.v. "Cardia"
- Cornelius Nepos, Lives of Eminent Commanders, "Miltiades", 1