|Millennium:||1st millennium BC|
|245 BC by topic|
|Gregorian calendar||245 BC|
|Ab urbe condita||509|
|Ancient Egypt era||XXXIII dynasty, 79|
|- Pharaoh||Ptolemy III Euergetes, 2|
|Ancient Greek era||133rd Olympiad, year 4|
|Balinese saka calendar||N/A|
|Chinese calendar||乙卯年 (Wood Rabbit)|
2452 or 2392
— to —
丙辰年 (Fire Dragon)
2453 or 2393
|Coptic calendar||−528 – −527|
|Ethiopian calendar||−252 – −251|
|- Vikram Samvat||−188 – −187|
|- Shaka Samvat||N/A|
|- Kali Yuga||2856–2857|
|Iranian calendar||866 BP – 865 BP|
|Islamic calendar||893 BH – 892 BH|
|Minguo calendar||2156 before ROC|
|Seleucid era||67/68 AG|
|Thai solar calendar||298–299|
−118 or −499 or −1271
— to —
−117 or −498 or −1270
Year 245 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Buteo and Bulbus (or, less frequently, year 509 Ab urbe condita). The denomination 245 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.
- Babylon and Susa fall to the Egyptian armies of Ptolemy III.
- Following a long engagement, Ptolemy III marries Berenice II, the daughter of Magas, king of Cyrene; thereby reuniting Egypt and Cyrenaica.
- After the death of his nephew, Alexander of Corinth, Antigonus II gives Nicaea, Alexander's widow, to his son Demetrius in marriage. Through this action, Antigonus II regains Corinth which has been independent while under the rule of Alexander of Corinth.
- Aratus of Sicyon is elected general (strategos) of the Achaean League.
- Apollonius of Rhodes, Greek poet, grammarian, and author of the Argonautica, an epic in four books on the voyage of the Argonauts (b. c. 295 BC)