Alexander IV (323–309 BC), posthumous son of Alexander the Great and his wife Roxana of Bactria and grandson of Philip II of Macedon.
Since Roxana was pregnant when Alexander died in June 323 BC, and the sex of the baby was unknown, there was debate over who should succeed Alexander. The infantry supported Alexander's half-brother Philip Arrhidaeus, but Perdiccas, commander of the Companion cavalry, persuaded them to wait since Roxana's child could be male.
The compromise solution saw Perdiccas rule the empire as regent, with Philip as a figurehead without real power.
After he was born, Alexander joined Philip Arrhidaeus as joint ruler of the empire. Perdiccas remained the regent until his senior officers assassinated him in May or June 321 or 320 after a military failure in Egypt and a mutiny in the army.
Antipater became the new regent after the Partition of Triparadisus and brought Roxana and the two kings to Macedon, leaving Egypt and Asia under the control of Alexander the Great's former generals.
When Antipater died in 319, he bequeathed the regency to the Macedonian general Polyperchon, who had served under Alexander the Great and his father rather than his son, Cassander.
Cassander responded by allying with Ptolemy Soter, Antigonus and Philip Arrhidaeus' ambitious wife Eurydice, which declared war against Polyperchon and his allies Eumenes and Olympias.
While Polyperchon was successful at first, Antigonus destroyed his fleet in 318, and Cassander took control of Macedon. Polyperchon fled to Epirus, followed by Roxana and the young Alexander. A few months later, Olympias persuaded her relative Aeacides of Epirus to invade Macedon with Polyperchon. When Olympias took the field, Eurydice's army refused to fight against Alexander the Great's mother and defected to her side.
When Polyperchon and Aeacides retook Macedon, Philip and Eurydice were captured and executed in December 317
That left Alexander IV as king, with Olympias in effective control as his regent.
When Cassander returned to conquer Macedon the following year, Olympias was executed. Alexander and his mother were taken prisoner and held in Amphipolis under the supervision of Glaucias.
The peace treaty that ended the Third Diadoch War, agreed to by Cassander, Antigonus, Ptolemy, and Lysimachus in 311, explicitly stated that Alexander IV would succeed Cassander as the ruler when he came of age.
When the boy turned fourteen, and his supporters declared he should exercise full power as a regent was no longer necessary, Cassander's response was decisive.
He commanded Glaucias to assassinate Alexander and his mother secretly. Both were poisoned, probably late in the summer of 309. His alleged half-brother Heracles was killed shortly after that.
After Alexander was buried secretly, Cassander and the other significant players maintained the convenient fiction that he was still alive until around 305.