|Millennium:||1st millennium BC|
|373 BC by topic|
|Gregorian calendar||373 BC|
|Ab urbe condita||381|
|Ancient Egypt era||XXX dynasty, 8|
|- Pharaoh||Nectanebo I, 8|
|Ancient Greek era||101st Olympiad, year 4|
|Balinese saka calendar||N/A|
|Chinese calendar||丁未年 (Fire Goat)|
2324 or 2264
— to —
戊申年 (Earth Monkey)
2325 or 2265
|Coptic calendar||−656 – −655|
|Ethiopian calendar||−380 – −379|
|- Vikram Samvat||−316 – −315|
|- Shaka Samvat||N/A|
|- Kali Yuga||2728–2729|
|Iranian calendar||994 BP – 993 BP|
|Islamic calendar||1025 BH – 1024 BH|
|Minguo calendar||2284 before ROC|
|Thai solar calendar||170–171|
−246 or −627 or −1399
— to —
−245 or −626 or −1398
Year 373 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Third year without Tribunate or Consulship (or, less frequently, year 381 Ab urbe condita). The denomination 373 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 King Artaxerxes II launches an invasion of Egypt to bring that country back under Persian rule. The invasion is led by Pharnabazus. After initial successes, the Greek mercenaries fighting for the Persians push on towards Memphis. However, King Nectanebo I is able to gather his forces and repulse the Persian invasion.
- Iphicrates leads an Athenian expedition which successfully relieves Corcyra of a Spartan siege.
- The ancient Greek city of Helike is destroyed by a massive earthquake and tsunami.
- The Temple of Apollo in Delphi is destroyed by the earthquake.