- The Eurypontid King of Sparta, Agis IV, is called away from Sparta when Aratus of Sicyon, temporarily Sparta's ally, requests Agis' aid in his war against the Aetolians. Upon his return, Agis finds that his supporters are discontented with the rule of his uncle, Agesilaus, and are disillusioned by the delay in implementing the Agis IV's reforms. As a result, the Agiad king of Sparta, Leonidas II, gains power, supported by mercenaries. Rather than engage in a war with Leonidas, Agis takes sanctuary in a temple, but is enticed out, summarily tried and then executed, along with his mother and grandmother.
- Archidamus V, son of the Spartan King, Eudamidas II, and grandson of Archidamus IV, flees to Messenia after the murder of his brother Agis IV.
- As general of the Achaean League, Aratus of Sicyon defeats the Aetolians at Pellene and then pursues a policy of establishing democracies in the Peloponnese.
- March 10 — The Carthaginian fleet sent to relieve the Roman blockade of the Sicilian cities of Lilybaeum and Drepanum is totally defeated near the Aegates Islands off western Sicily by the Roman fleet led by Roman consul and commander, Gaius Lutatius Catulus. The result is a decisive Roman victory which forces an end to the protracted First Punic War, to Rome's distinct advantage.
- The Carthaginians under Hamilcar Barca are forced to accept severe peace terms and agree to evacuate Sicily. As part of the treaty with Rome, Carthage agrees to abandon all its claims on Sicily, to refrain from sailing her warships in Italian waters and to pay an indemnity of 3,200 talents. However, the Carthaginian army is allowed to return home with its arms. Rome is now the dominant power in the Western Mediterranean basin.
- A mercenary army of some 20,000 is transported from Sicily to Carthaginian territory, by Carthaginian commander, Gesco. On arrival in Carthaginian territory, the mercenaries submit a demand to Hanno the Great for payment of their contracts. Hanno attempts, unsuccessfully, to convince the mercenaries to accept smaller payments due to Carthage's impoverished post-war conditions. Negotiations break down. The mercenaries take up arms, march on Tunis, occupy it, and threaten Carthage directly.
- Given their strong position, the mercenaries inflate their demands and demand payment for the non-mercenary Libyan conscripts in the army as well. Gesco is sent to negotiate with the mercenaries at Tunis.