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|Millennium:||1st millennium BC|
|381 BC by topic|
|Gregorian calendar||381 BC
|Ab urbe condita||373|
|Ancient Egypt era||XXIX dynasty, 18|
|- Pharaoh||Hakor, 13|
|Ancient Greek era||99th Olympiad, year 4|
|Balinese saka calendar||N/A|
|Chinese calendar||己亥年 (Earth Pig)
2316 or 2256
— to —
庚子年 (Metal Rat)
2317 or 2257
|Coptic calendar||−664 – −663|
|Ethiopian calendar||−388 – −387|
|- Vikram Samvat||−324 – −323|
|- Shaka Samvat||N/A|
|- Kali Yuga||2720–2721|
|Iranian calendar||1002 BP – 1001 BP|
|Islamic calendar||1033 BH – 1032 BH|
|Minguo calendar||2292 before ROC
|Thai solar calendar||162–163|
−254 or −635 or −1407
— to —
−253 or −634 or −1406
Year 381 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Tribunate of Camillus, Albinus, Albinus, Medullinus, Flavus and Ambustus (or, less frequently, year 373 Ab urbe condita). The denomination 381 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.
- The Persian generals Tiribazus and Orontes invade Cyprus, with an army far larger than any King Evagoras of Cyprus could raise. However, Evagoras manages to cut off this force from being resupplied, and the starving troops rebel. However, the war then turns in the Persians' favour when Evagoras' fleet is destroyed at the Battle of Citium (Larnaca, Cyprus). Evagoras flees to Salamis, where he manages to conclude a peace which allows him to remain nominally king of Salamis, though in reality he is a vassal of the Persian king.
- Sparta increases its hold on central Greece by reestablishing the city of Plataea, which Sparta has destroyed in 427 BC.
- The district of Tusculum is pacified after a revolt against Rome and conquered. After an expression of complete submission to Rome, Tusculum becomes the first "municipium cum suffragio", and thenceforth the city continues to hold the rank of a municipium.
- Wu Qi, Chinese military general, Prime Minister of the State of Chu, also a servant of the State of Lu (born in Wei, 440 BC)