|Millennium:||1st millennium BC|
|307 BC by topic|
|Gregorian calendar||307 BC
|Ab urbe condita||447|
|Ancient Egypt era||XXXIII dynasty, 17|
|- Pharaoh||Ptolemy I Soter, 17|
|Ancient Greek era||118th Olympiad, year 2|
|Chinese calendar||癸丑年 (Water Ox)
2390 or 2330
— to —
甲寅年 (Wood Tiger)
2391 or 2331
|Coptic calendar||−590 – −589|
|Ethiopian calendar||−314 – −313|
|- Vikram Samvat||−250 – −249|
|- Shaka Samvat||N/A|
|- Kali Yuga||2794–2795|
|Iranian calendar||928 BP – 927 BP|
|Islamic calendar||957 BH – 955 BH|
|Minguo calendar||2218 before ROC
|Seleucid era||5/6 AG|
|Thai solar calendar||236–237|
Year 307 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Caecus and Violens (or, less frequently, year 447 Ab urbe condita). The denomination 307 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.
- Ptolemy founds the Museum and Library of Alexandria with the help of Demetrius Phalereus. Like Alexander the Great, Ptolemy has studied under Aristotle and staffs the museum with some 100 professors paid by the state.
- The governor (despot) of Athens for 10 years and supporter of Cassander, Demetrius Phalereus, is obliged to flee from Athens on the approach of the Macedonian prince, Demetrius Poliorcetes. Demetrius Phalereus settles in Alexandria in Egypt.
- Demetrius Poliorcetes re-establishes the old Athenian constitution. The grateful Athenians honour Antigonus and Demetrius as divine saviours (theoi soteres).
- Upon becoming ruler of Epirus, Pyrrhus allies himself with his brother-in-law, Demetrius Poliorcetes, son of Antigonus.
- The tyrant of Syracuse, Agathocles is forced to return to Syracuse to deal with growing unrest in his Sicilian dominions. Those of Agathocles' army that remain behind in Carthage are soon destroyed.
- The Carthaginian general Hamilcar fails to take Syracuse and is captured and killed.
- The city of Segesta in Sicily is destroyed by Agathocles.
- The Chinese King Wuling of Zhao reforms the military of the State of Zhao by putting more emphasis on cavalry over charioteers.
- Epicureanism, a system of philosophy based upon the teachings of Epicurus, is founded (approximate date).