285 BC

Year 285 BC was a year of the pre-Julian Roman calendar.

Millennium:	1st millennium BC
Centuries:	4th century BC – 3rd century BC – 2nd century BC
Decades:	310s BC  300s BC  290s BC  – 280s BC –  270s BC  260s BC  250s BC
Years:	288 BC 287 BC 286 BC – 285 BC – 284 BC 283 BC 282 BC

Egypt

• June 26 – Egypt's Ptolemy I Soter quits ruling. He is succeeded by his youngest son by his wife Berenice, Ptolemy II Philadelphus. He was co-regent for three years.
• A 110 metre tall lighthouse on the island of Pharos in Alexandria's harbour is completed. It is a landmark for ships in the eastern Mediterranean. Built by Sostratus of Cnidus for Ptolemy II of Egypt, it is one of the seven wonders of the ancient world. It is a technological triumph and is the archetype of all lighthouses since. A broad spiral ramp leads to the top, where a fire burns at night.

Seleucid Empire

• Demetrius Poliorcetes is left by his troops and surrenders to Seleucus at Cilicia, where Seleucus keeps him a prisoner.

Deaths

• Dicaearchus, Greek philosopher, cartographer, geographer, mathematician and author (b. c. 350 BC)