255 BCCenturies: 4th century BC - 3rd century BC - 2nd century BC
- Battle of Tunes, the Carthaginians under Xanthippus, a Greek mercenary, defeat the Romans under Marcus Atilius Regulus, who is captured.
- Diodotus revolts from Antiochus II Theos, ruler of the Seleucid Empire, establishing the kingdom of Bactria. (approximate date)
- East Zhou Hui Wang becomes the last claimant King of the Zhou Dynasty of China.
- Zhao Xiang Wang becomes the first King of the Qin Dynasty of China.