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|Millennium:||1st millennium BC|
|371 BC by topic|
|Gregorian calendar||371 BC
|Ab urbe condita||383|
|Ancient Egypt era||XXX dynasty, 10|
|- Pharaoh||Nectanebo I, 10|
|Ancient Greek era||102nd Olympiad, year 2|
|Balinese saka calendar||N/A|
|Chinese calendar||己酉年 (Earth Rooster)
2326 or 2266
— to —
庚戌年 (Metal Dog)
2327 or 2267
|Coptic calendar||−654 – −653|
|Ethiopian calendar||−378 – −377|
|- Vikram Samvat||−314 – −313|
|- Shaka Samvat||N/A|
|- Kali Yuga||2730–2731|
|Iranian calendar||992 BP – 991 BP|
|Islamic calendar||1022 BH – 1021 BH|
|Minguo calendar||2282 before ROC
|Thai solar calendar||172–173|
−244 or −625 or −1397
— to —
−243 or −624 or −1396
|Wikimedia Commons has media related to 371 BC.|
Year 371 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Fifth year without Tribunate or Consulship (or, less frequently, year 383 Ab urbe condita). The denomination 371 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.
- A fresh peace congress is summoned at Sparta. At the peace conference, the Spartan King Agesilaus II (with the support of Athens) refuses to allow the Thebans to sign the treaty on behalf of all Boeotia. The Theban statesman Epaminondas, who is boeotarch (one of the five magistrates of the Boeotian federation), maintains Thebes' position, even when it leads to the exclusion of Thebes from the peace treaty.
- Thebes' actions at the peace congress lead to a war between Sparta and Thebes. The Spartans have an army stationed on Thebes' western frontier, waiting to follow up their diplomatic success by a crushing military attack. However, at the Battle of Leuctra, the Theban generals, Epaminondas and Pelopidas, win a decisive victory over the Spartans under the other Spartan king, Cleombrotus I (who is killed in the battle). Epaminondas wins the battle with a tactical innovation which involves striking the enemy first at their strongest, instead of their weakest, point, with such crushing force that the attack is irresistible. As a result of this battle, the Boeotian federation is saved.
- Athens does not welcome the Theban victory, fearing the rising aggressiveness of Thebes. After the Theban victory, the old alliance between the Persians and the Thebans is restored.
- With the unexpected defeat of Sparta by the Thebans, the Arcadians decide to re-assert their independence. They rebuild Mantinea, form an Arcadian League and build a new federal city, Megalopolis.
- Agesipolis II succeeds his father Cleombrotus I as king of Sparta.
- It is suggested that the original comet associated with the Kreutz Sungrazers family of comets passes perihelion at this time. It is thought to have been observed by Aristotle and Ephorus during this year.