|Millennium:||1st millennium BC|
|256 BC by topic|
|Gregorian calendar||256 BC|
|Ab urbe condita||498|
|Ancient Egypt era||XXXIII dynasty, 68|
|- Pharaoh||Ptolemy II Philadelphus, 28|
|Ancient Greek era||131st Olympiad (victor)¹|
|Balinese saka calendar||N/A|
|Chinese calendar||甲辰年 (Wood Dragon)|
2442 or 2235
— to —
乙巳年 (Wood Snake)
2443 or 2236
|Coptic calendar||−539 – −538|
|Ethiopian calendar||−263 – −262|
|- Vikram Samvat||−199 – −198|
|- Shaka Samvat||N/A|
|- Kali Yuga||2845–2846|
|Iranian calendar||877 BP – 876 BP|
|Islamic calendar||904 BH – 903 BH|
|Minguo calendar||2167 before ROC|
|Seleucid era||56/57 AG|
|Thai solar calendar||287–288|
−129 or −510 or −1282
— to —
−128 or −509 or −1281
Year 256 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Longus and Caedicius/Regulus (or, less frequently, year 498 Ab urbe condita). The denomination 256 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.
- Rome aims for a quick end to hostilities in the First Punic War and decides to invade the Carthaginian colonies in Northern Africa to force the enemy to accept terms. A major fleet is built, including transports for the army and its equipment, and warships for their protection. Carthage under Hamilcar tries to intervene but a force under the Roman general and consul Marcus Atilius Regulus and his colleague Lucius Manlius Vulso Longus defeat the Carthaginian fleet in the Battle of Cape Ecnomus off the southern coast of Sicily.
- Following the Battle of Cape Ecnomus, the Romans land an army near Carthage and begin ravaging the Carthaginian countryside. The Roman army soon forces the capitulation of Clupea, a town 40 miles (64 kilometres) east of Carthage. After setting up Roman defenses for the city, the two consuls receive instructions from Rome that Vulso is to set sail for Rome, taking most of the fleet with him. Regulus, on the other hand, is to stay with the infantry and cavalry to finish the war.
- The Great Wall of China construction starts.
- Luoyang falls without much resistance to the armies of the Qin, ending the reign of the emperor Zhou Nan Wang. Although a successor was appointed as Dong Zhou Hui Wang, traditionally in Chinese history this is considered the end of the Zhou dynasty.
- The Du Jiang Yan Irrigation System is constructed, ending flooding and irrigating thousands of square miles of land through an ingeniously designed system.
- Casson, Lionel (1995). Ships and Seamanship in the Ancient World (1st ed.). Baltimore, Maryland: Johns Hopkins University Press. ISBN 0-8018-5130-0.
- "Clupea - Livius". www.livius.org. Retrieved December 1, 2022.
- Centre, UNESCO World Heritage. "The Great Wall". UNESCO World Heritage Centre. Retrieved December 1, 2022.
- Qian, Sima (1995). The Grand Scribe's Records, Vol. 1: The Basic Annals of Pre-Han China (1st ed.). Bloomington, Indiana: Indiana University Press.
- Zhang, Kan (2006). World Heritage in China. Guangzhou: The Press of South China University of Technology. ISBN 7-5623-2390-9.
- "Gaozu | emperor of Han dynasty | Britannica". www.britannica.com. Retrieved December 1, 2022.
- "Wuwang | ruler of Zhou | Britannica". www.britannica.com. Retrieved December 1, 2022.