Year 157 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Caesar and Orestes (or, less frequently, year 597 Ab urbe condita). The denomination 157 BC for this year has been used since the early medieval period, when the Anno Dominicalendar era became the prevalent method in Europe for naming years.
The Carthaginians, prevented by their treaty with Rome from engaging in armed resistance, but equally guaranteed against any loss of territory, appeal to Rome against the depredations of King Masinissa of Numidia. The Roman censorMarcus Porcius Cato heads a commission which arbitrates a truce between Carthage and her former ally, Masinissa.
During his time in Carthage, Cato is so struck by the evidence of Carthaginian prosperity that he is convinced that the security of Rome now depends on the annihilation of Carthage. From this time on, Cato keeps repeating the cry "Ceterum censeo Carthaginem esse delendam" ("Moreover, I advise that Carthage must be destroyed") at the end of all his speeches, no matter what subject they concern.
After Ariarathes V has been deposed from the Cappadocian throne by the Seleucid king Demetrius I Soter and has fled to Rome, the new king of Cappadocia, Orophernes, sends two ambassadors to Rome to join the Seleucid emissaries of Demetrius in opposing Ariarathes V's return to power. Despite their efforts, Ariarathes V is restored to his throne by the Romans. However, Rome allows Orophernes to reign jointly with him. The joint government, however, does not last long, as Ariarathes V becomes sole king of Cappadocia shortly afterwards.
Gaius Marius, Roman general and politician who will be elected consul seven times; he will also introduce major reforms to the Roman army, authorising recruitment of landless citizens and reorganising the structure of the legions (d. 86 BC)
Sanatruces (also known as Sinatruces or Sanatruk), King of Parthia who will rule the Parthian Empire from around 77 BC (approximate date) (d. c. 70 BC)