The term Hellenistic or Hellenism (derived from ????? Héll?n, the Greeks' word for themselves) was established by the German historian Johann Gustav Droysen to refer to the shift from a culture dominated by ethnic Greeks to a culture dominated by Greek-speakers of various ethnicities, and from the political dominance of the city-state to that of larger monarchies. In this period the traditional Greek culture was changed by strong Eastern influences, especially Persian, in aspects of religion and government. Cultural centers shifted away from mainland Greece, to Pergamon, Rhodes, Antioch and Alexandria.

Modern historians see the death of Alexander the Great in 323 BC as the beginning of the Hellenistic period. Alexander and the Macedonians conquered the eastern Mediterranean, Mesopotamia, and the Iranian plateau, and invaded India. Following Alexander's death, there was a struggle for the succession, known as the wars of the Diadochi (Greek for successors). These ended in 281 BC with the establishment of four large territorial states:

  • the Ptolemaic dynasty in Egypt based at Alexandria
  • the Seleucid dynasty in Syria and Mesopotamia based at Antioch
  • the Antigonid dynasty in Macedonia and the mainland of Greece
  • the Attalid dynasty in Anatolia based at Pergamum
  • His successors held on to the territory west of the Tigris for some time and controlled the eastern Mediterranean until the Roman Republic took control in the 2nd and 1st centuries BC. Most of the east was eventually overrun by the Parthians, but Hellenistic culture held on in distant locations, like the Greco-Bactrian kingdom in Bactria, or the Indo-Greek kingdom in northern India, or the Cimmerian Bosporus.

It must also be added that Hellenism made considerable inroads also in monarchies governed by kings of Persian or Thracian origin, as was the case with Bithynia, Cappadocia and Pontus.

The end of the Hellenistic period is generally seen as 31 BC, when the power of Ptolemaic Egypt was smashed by the Romans at the Battle of Actium. Shortly thereafter, the independence of the Ptolemies was at an end with the suicide of Cleopatra and the annexation of Egypt by Caesar Augustus.