|Millennium:||1st millennium BC|
|306 BC by topic|
|Gregorian calendar||306 BC|
|Ab urbe condita||448|
|Ancient Egypt era||XXXIII dynasty, 18|
|- Pharaoh||Ptolemy I Soter, 18|
|Ancient Greek era||118th Olympiad, year 3|
|Balinese saka calendar||N/A|
|Chinese calendar||甲寅年 (Wood Tiger)|
2391 or 2331
— to —
乙卯年 (Wood Rabbit)
2392 or 2332
|Coptic calendar||−589 – −588|
|Ethiopian calendar||−313 – −312|
|- Vikram Samvat||−249 – −248|
|- Shaka Samvat||N/A|
|- Kali Yuga||2795–2796|
|Iranian calendar||927 BP – 926 BP|
|Islamic calendar||955 BH – 954 BH|
|Minguo calendar||2217 before ROC|
|Seleucid era||6/7 AG|
|Thai solar calendar||237–238|
−179 or −560 or −1332
— to —
−178 or −559 or −1331
Year 306 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Tremulus and Arvina (or, less frequently, year 448 Ab urbe condita). The denomination 306 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.
- Demetrius Poliorcetes lands on Cyprus and besieges Menelaus, brother of Egypt's ruler, Ptolemy I Soter, at Salamis. Ptolemy I Soter, coming to his brother's aid, is decisively defeated in the Battle of Salamis. The battle completely destroys the naval power of Egypt and results in the capture of Cyprus by Demetrius Poliorcetes This gives Demetrius Poliorcetes' father, Antigonus I Monophthalmus, control of the Aegean and the eastern Mediterranean.
- Antigonus I Monophthalmus uses the occasion to assume the title of king, vacant since the murder of Alexander IV of Macedon. He immediately declares Demetrius Poliorcetes his co-ruler.
- Antigonus I Monophthalmus proclaims himself king of Asia Minor and northern Syria thus commencing the Antigonid dynasty. Antigonus I Monophthalmus appoints Demetrius Poliorcetes king and co-regent.
- A peace agreement is reached between Syracuse and Carthage. The peace restricts Carthaginian power in Sicily to the area west of the Halycus (Platani) River. This agreement allows the tyrant of Syracuse, Agathocles, to strengthen his rule over the Greek cities of Sicily.
- Antigonus I Monophthalmus tries to follow up his victory in Cyprus by invading Egypt with a large army and a formidable fleet. But Ptolemy I Soter successfully holds the frontier against him. However, the year's events mean that Ptolemy I Soter no longer engages in overseas expeditions against Antigonus I Monophthalmus.
- A four-drachma coin, picturing Alexander the Great, is issued by Lysimachos from this time until 281 BC. At least one of them is now preserved at the British Museum in London.