|Millennium:||1st millennium BC|
|388 BC by topic|
|Gregorian calendar||388 BC|
|Ab urbe condita||366|
|Ancient Egypt era||XXIX dynasty, 11|
|- Pharaoh||Hakor, 6|
|Ancient Greek era||98th Olympiad (victor)¹|
|Balinese saka calendar||N/A|
|Chinese calendar||壬辰年 (Water Dragon)|
2309 or 2249
— to —
癸巳年 (Water Snake)
2310 or 2250
|Coptic calendar||−671 – −670|
|Ethiopian calendar||−395 – −394|
|- Vikram Samvat||−331 – −330|
|- Shaka Samvat||N/A|
|- Kali Yuga||2713–2714|
|Iranian calendar||1009 BP – 1008 BP|
|Islamic calendar||1040 BH – 1039 BH|
|Minguo calendar||2299 before ROC|
|Thai solar calendar||155–156|
−261 or −642 or −1414
— to —
−260 or −641 or −1413
Year 388 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Tribunate of Capitolinus, Fidenas, Iullus, Corvus, Flavus and Rufus (or, less frequently, year 366 Ab urbe condita). The denomination 388 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.
- King Agesipolis I leads a Spartan army against Argos. Since no Argive army challenges him, he plunders the countryside for a time, and then, after receiving several unfavorable omens, returns to Sparta.
- The Athenian general, Thrasybulus, sails to Lesbos, where, with the support of the Mytileneans, he defeats the Spartan forces on the island and wins over a number of cities. While still on Lesbos, however, Thrasybulus is killed by raiders from the city of Aspendus where his financial exactions have made him unpopular.
- Concerned about the revival of Athenian imperialist ambitions, the Persian King Artaxerxes II and King Agesilaus II of Sparta enter into an alliance. Sparta also seeks and gains the support of Dionysius I of Syracuse.
- Plato, having left Athens on Socrates' death to visit Megara and possibly Egypt, travels to Syracuse at the invitation of Dionysius I's brother-in-law Dion.
- Aristophanes' play Plutus is performed.
- Thrasybulus, Athenian general who helped overthrow the Thirty Tyrants