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 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. This gives Demetrius' father, Antigonus I Monophthalmus, control of the Aegean and the eastern Mediterranean.^[1]

• Antigonus I Monophthalmus proclaims himself king of Asia Minor and northern Syria thus commencing the Antigonid dynasty. He appoints his son Demetrius king and co-regent.^[2]

• Antigonus Monophthalmus tries to follow up his victory in Cyprus by invading Egypt with a large army and a formidable fleet, but Ptolemy Soter 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.

• The Samnites take Sora and Calatia, cities allied to the Romans, and enslave their inhabitants.^[3][4]
• The Romans invade Iapygia and begin a siege of Silvium (garrisoned by the Samnites). Eventually, they take the city by storm, taking 5,000 prisoners. After the Siege of Silvium they invade Samnium itself, pillaging the countryside for five months.^[5][4]

• Agathocles tries to negotiate a settlement with Deinocrates, the leader of the exiles, but the latter refuses, forcing Agathocles to continue the war for dominance over eastern Sicily.^[6]
• 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 in the east of Sicily.

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• Philip, youngest son of Antigonus Monophthalmus.^[7][8]
• Dionysius of Heraclea, tyrant of Heraclea Pontica.^[9][10]