|Millennium:||1st millennium BC|
|Centuries:||5th century BC – 4th century BC – 3rd century BC|
|Decades:||330s BC 320s BC 310s BC – 300s BC – 290s BC 280s BC 270s BC|
|Years:||309 BC 308 BC 307 BC – 306 BC – 305 BC 304 BC 303 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|
|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||2796–2797|
|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|
|Wikimedia Commons has media related to 306 BC.|
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, 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. This gives Demetrius Poliorcetes' father, Antigonus I Monophthalmus, control of the Aegean and the eastern Mediterranean.
- Antigonus uses the occasion to assume the title of king, vacant since the murder of Alexander IV of Macedon. He immediately declares Demetrius his co-ruler.
- Antigonus proclaims himself king of Asia Minor and northern Syria thus commencing the Antigonid dynasty. Antigonus 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 tries to follow up his victory in Cyprus by invading Egypt with a large army and a formidable fleet. But Ptolemy successfully holds the frontier against him. However, the year's events mean that Ptolemy no longer engages in overseas expeditions against Antigonus.
- 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.