The history of the Hellenistic world after Alexander's death (323 BC) is one of the most complex and underappreciated periods in ancient history. The decades of conflict among the Diadochi (successors) produced not chaos but a relatively stable multipolar system by about 280 BC that governed much of the known world for the next century and a half.

The Ptolemaic kingdom in Egypt was the most durably successful of the successor states, lasting from 305 BC until Cleopatra VII's death in 30 BC — nearly three centuries. Its stability rested on the extraordinary agricultural productivity of the Nile valley, which provided a revenue base that allowed the Ptolemies to sustain a professional army and a lavish court without dependence on tribute from conquered territories.

The Seleucid empire in Asia was always less stable: too large, too diverse, and pressed on multiple frontiers. The gradual loss of the eastern satrapies to the Parthians (from the mid-3rd century BC onward) and of Anatolia to Rome reduced it to a Syrian rump state by the 1st century BC.

The Antigonid kingdom in Macedon and its contested hegemony over mainland Greece represents the closest continuation of the classical period. The federal leagues — the Achaean and Aetolian — that provided counterweights to Antigonid power are interesting experiments in Greek interstate organization that have received less attention than the earlier polis system.