|Millennium:||1st millennium BC|
|274 BC by topic|
|Gregorian calendar||274 BC|
|Ab urbe condita||480|
|Ancient Egypt era||XXXIII dynasty, 50|
|- Pharaoh||Ptolemy II Philadelphus, 10|
|Ancient Greek era||126th Olympiad, year 3|
|Balinese saka calendar||N/A|
|Chinese calendar||丙戌年 (Fire Dog)|
2423 or 2363
— to —
丁亥年 (Fire Pig)
2424 or 2364
|Coptic calendar||−557 – −556|
|Ethiopian calendar||−281 – −280|
|- Vikram Samvat||−217 – −216|
|- Shaka Samvat||N/A|
|- Kali Yuga||2827–2828|
|Iranian calendar||895 BP – 894 BP|
|Islamic calendar||923 BH – 921 BH|
|Minguo calendar||2185 before ROC|
|Seleucid era||38/39 AG|
|Thai solar calendar||269–270|
−147 or −528 or −1300
— to —
−146 or −527 or −1299
Year 274 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Dentatus and Merenda (or, less frequently, year 480 Ab urbe condita). The denomination 274 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.
- Pyrrhus returns from Italy and Sicily and invades Macedonia defeating Antigonus II Gonatas at the Battle of the Aous and conquering Upper Macedonia and Thessaly while Antigonus holds onto the coastal Macedonian towns. Antigonus' troops desert him and Pyrrhus is declared King of Macedonia.
- The Romans under Manius Curius Dentatus conquer the Lucanians.
- Magas of Cyrene marries Apama, the daughter of Antiochus and uses his marital alliance to foment a pact to invade Egypt. He opens hostilities against his half brother Ptolemy II, by declaring his province of Cyrenaica to be independent and then attacks Egypt from the west as Antiochus I takes the Egyptian controlled areas in coastal Syria and southern Anatolia, after which he attacks Palestine.
- Magas has to stop his advance against Ptolemy II due to an internal revolt by the Libyan Marmaridae nomads.