320 BC

By place

Macedonian Empire

• Alexander the Great's various generals control different parts of Alexander's empire. Ptolemy controls Egypt, Seleucus controls Babylon and Syria, Antipater and his son Cassander control Macedon and Greece, Antigonus controls Phrygia and other parts of Asia Minor, Lysimachus controls Thrace and Pergamum and Eumenes controls the Cappadocia and Pontus areas.
• Judea and Syria are annexed by Ptolemy and he gives Judea a large measure of self-government.
• Eudemus makes himself master of the territories of the Indian king Porus, and treacherously puts that monarch to death.

  China

• Zhou Shen Jing Wang becomes King of the Zhou Dynasty of China.

  By topic

Biology

• Theophrastus begins the systematic study of botany.

  Demography

• Alexandria in Macedonian Egypt becomes the largest city of the world, taking over the lead from Babylon in Macedonian Babylonia.