|Millennium:||1st millennium BC|
|239 BC by topic|
|Gregorian calendar||239 BC|
|Ab urbe condita||515|
|Ancient Egypt era||XXXIII dynasty, 85|
|- Pharaoh||Ptolemy III Euergetes, 8|
|Ancient Greek era||135th Olympiad, year 2|
|Balinese saka calendar||N/A|
|Chinese calendar||辛酉年 (Metal Rooster)|
2458 or 2398
— to —
壬戌年 (Water Dog)
2459 or 2399
|Coptic calendar||−522 – −521|
|Ethiopian calendar||−246 – −245|
|- Vikram Samvat||−182 – −181|
|- Shaka Samvat||N/A|
|- Kali Yuga||2862–2863|
|Iranian calendar||860 BP – 859 BP|
|Islamic calendar||886 BH – 885 BH|
|Minguo calendar||2150 before ROC|
|Seleucid era||73/74 AG|
|Thai solar calendar||304–305|
−112 or −493 or −1265
— to —
−111 or −492 or −1264
Year 239 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Turrinus and Falto (or, less frequently, year 515 Ab urbe condita). The denomination 239 BC for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
- Concerned that Hamilcar Barca's leniency in pardoning those who he has captured who have participated in the Mercenary War will encourage others to defect, Mathos and Spendius order the mutilation and execution of "about seven hundred" Carthaginian prisoners, including Gesco. With the mercenaries jointly guilty of these atrocities, defectors dare not face Carthaginian justice under Hamilcar.
- Carthage is besieged by the mercenary armies, while the city of Utica revolts and attempts to secede from Carthage. Carthage appeals to Hiero II of Syracuse and to Rome for aid against the mercenaries. However, the mercenary leaders reject the efforts of Roman mediators.
- Sardinia revolts against Carthage and Rome takes the opportunity to annex the island.
- Antigonus II, King of Macedonia, dies and is succeeded by his son, Demetrius II.
- With Aetolia now as its ally, the Achaean League under the command of Aratus of Sicyon repeatedly attack Athens and Argos.
- Seleucus II's brother Antiochus Hierax, who is governor of Seleucid Anatolia, sends an army into Syria ostensibly to assist Seleucus but actually to seize the rest of the empire. After achieving peace with Egypt, Seleucus II promptly invades Anatolia and begins the "War of the Brothers".
- Diodotus of Bactria defeats an army of Parthians. He dies shortly thereafter and is succeeded by his son Diodotus II.
- Haemosu, who is a descendant of the people of the empire of Gojoseon, establishes the ancient Korean kingdom of Bukbuyeo in modern-day Manchuria.
- Antigonus II Gonatas, king of Macedon from 277 BC who has rebuilt his kingdom's power and established its hegemony over Greece (b. c. 319 BC)
- Diodotus I, king of the Greco-Bactrian Kingdom (b. c. 285 BC)
- Huanhui of Han, Chinese king of the Han State