|Millennium:||1st millennium BC|
|188 BC by topic|
|Gregorian calendar||188 BC
|Ab urbe condita||566|
|Ancient Egypt era||XXXIII dynasty, 136|
|- Pharaoh||Ptolemy V Epiphanes, 16|
|Ancient Greek era||148th Olympiad (victor)¹|
|Balinese saka calendar||N/A|
|Chinese calendar||壬子年 (Water Rat)
2509 or 2449
— to —
癸丑年 (Water Ox)
2510 or 2450
|Coptic calendar||−471 – −470|
|Ethiopian calendar||−195 – −194|
|- Vikram Samvat||−131 – −130|
|- Shaka Samvat||N/A|
|- Kali Yuga||2913–2914|
|Iranian calendar||809 BP – 808 BP|
|Islamic calendar||834 BH – 833 BH|
|Minguo calendar||2099 before ROC
|Seleucid era||124/125 AG|
|Thai solar calendar||355–356|
Year 188 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Messalla and Salinator (or, less frequently, year 566 Ab urbe condita). The denomination 188 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 leader of the Achaean League, Philopoemen, enters northern Laconia with his army and a group of Spartan exiles. His army demolishes the wall that the former tyrant of Sparta, Nabis, has built around Sparta. Philopoemen then restores Spartan citizenship to the exiles and abolishes Spartan law, introducing Achaean law in its place. Sparta's role as a major power in Greece ends, while the Achaean League becomes the dominant power throughout the Peloponnese.
- The continuing quarrels among the Greek cities and leagues increases the conviction in Rome that there will be no peace in Greece until Rome takes full control.
- Through the peace treaty of Apamea (in Phrygia), the Romans force the Seleucid king, Antiochus III, to surrender all his Greek and Anatolian possessions as far east as the Taurus Mountains, to pay 15,000 talents over a period of 12 years and to surrender to Rome the former Carthaginian general Hannibal, his elephants and his fleet, and furnish hostages, including the king's eldest son, Demetrius. Rome is now the master of the eastern Mediterranean while Antiochus III's empire is reduced to Syria, Mesopotamia, and western Iran.
- Hannibal flees via Crete to the court of King Prusias I of Bithynia who is engaged in warfare with Rome's ally, King Eumenes II of Pergamum.
- Following the peace of Apamea, Eumenes II receives the provinces of Phrygia, Lydia, Lycia, Pisidia, and Pamphylia from his Roman allies, as the Romans have no desire to actually administer territory in Hellenistic Anatolia but want to see a strong, friendly state in Anatolia as a buffer zone against any possible Seleucid expansion in the future.
- Jing of Han, emperor of the Chinese Han Dynasty, who will rule from 156 BC. During his reign, he will fight to curtail of power of the Chinese feudal princes (d. 141 BC)