|Millennium:||1st millennium BC|
|308 BC by topic|
|Gregorian calendar||308 BC
|Ab urbe condita||446|
|Ancient Egypt era||XXXIII dynasty, 16|
|- Pharaoh||Ptolemy I Soter, 16|
|Ancient Greek era||118th Olympiad (victor)¹|
|Chinese calendar||壬子年 (Water Rat)
2389 or 2329
— to —
癸丑年 (Water Ox)
2390 or 2330
|Coptic calendar||−591 – −590|
|Ethiopian calendar||−315 – −314|
|- Vikram Samvat||−251 – −250|
|- Shaka Samvat||N/A|
|- Kali Yuga||2793–2794|
|Iranian calendar||929 BP – 928 BP|
|Islamic calendar||958 BH – 957 BH|
|Minguo calendar||2219 before ROC
|Seleucid era||4/5 AG|
|Thai solar calendar||235–236|
Year 308 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Mus and Rullianus (or, less frequently, year 446 Ab urbe condita). The denomination 308 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 crosses from Asia Minor into Greece, where he takes possession of Corinth, Sicyon and Megara.
- The Second Samnite War escalates when the tribes of the central Apennines, the Umbrians, Picentini, and Marsians join the war against Rome. However, Rome is able to control the uprising.
- The Etruscans sue for peace with Rome, which is granted by the Romans on severe terms.
- Cleopatra of Macedon, sister of Alexander the Great and daughter of King Philip II of Macedon and Olympias (b. c. 356 BC)