Year 145 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Aemilianus and Mancinus (or, less frequently, year 609 Ab urbe condita). The denomination 145 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.

• In the Battle of Antioch, Ptolemy VI Philometor defeats the Seleucid usurper Alexander Balas, but dies in the battle.

• Ptolemy VII becomes king of Egypt briefly, then is assassinated by Ptolemy VIII the following year.^[1]

• Hipparchus determines the length of the tropical year.

• Sima Qian, Chinese historian (or 135 BC) (d. 86 BC)^[2]

• Alexander Balas (assassinated)
• Ptolemy VI of Egypt (killed in battle) (b. c. 186 BC)