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 Dominicalendar era became the prevalent method in Europe for naming years.
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.