• King of Macedon
• Preceded by: Antipater II of Macedon (Antipatrid dynasty)
• Succeeded by: Demetrius I of Macedon

Antigonus I Monophthalmos ("the One-eyed") (382 BC - 301 BC) was a Macedonian nobleman, general, and satrap under Alexander the Great. He was a major figure in the Wars of the Diadochi after Alexander's death. He established the Antigonid dynasty and declared himself King of Macedonia in 306 BC.

Antigonus was appointed governor of Greater Phrygia in 333 BC, and in the division of the provinces after Alexander's death in 323 BC he also received Pamphylia and Lycia from Perdiccas, regent of the empire. On Perdiccas's death in 321 BC, a new division of empire took place. Antigonus found himself entrusted with the command of the war against Eumenes, who had joined Perdiccas against the coalition of Antipater, Antigonus, Ptolemy, Craterus, and the other generals. Eumenes was defeated and forced to retire to the fortress of Nora in Cappadocia.

Polyperchon succeeded Antipater regent of the empire in 319 BC. Antigonus had set himself up as lord of all Asia, and, in conjunction with Cassander and Ptolemy, refused to recognize Polyperchon. Antigonus fought against Eumenes two great battles at Paraitacene in 317 BC and Gabiene in 316 BC, following which Eumenes was executed at Antigonus' order.

Antigonus again claimed authority over most Asia, seized the treasures at Susa and entered Babylon, of which Seleucus was governor. Seleucus fled to Ptolemy and entered into a league with him, Lysimachus and Cassander (315 BC) against Antigonus. In 314 BC Antigonus invaded Syria, under Ptolemy's control, and besieged Tyre for more than a year. His son Demetrius was defeated at the Battle of Gaza by Ptolemy in 312 BC and lost Babylonia.

Demetrius defeated Ptolemy at the naval battle of Salamis and conquered Cyprus in 306 BC. Following the victory Antigonus assumed the title king and bestowed the same upon his son, a declaration that he was claiming to be Alexander's heir. He now prepared a large army and a formidable fleet, the command of which he gave to Demetrius, and hastened to attack Ptolemy in his own dominions. His invasion of Egypt, however, proved a failure; he was unable to penetrate Ptolemy's defences and was obliged to retire. Demetrius in 305 BC attempted the reduction of Rhodes, which had refused to assist Antigonus against Egypt. The siege of Rhodes lasted a year and ended in 304 BC with a peace treaty.

The most powerful satraps of the empire, Cassander, Seleucus, Ptolemy and Lysimachus, responded to Antigonus's assumption of the royal title by proclaiming themselves also kings. Antigonus soon found himself at war with all four, largely because his territory shared borders with each of them. He demanded from Cassander the unconditional submission of Macedonia. Seleucus, Lysimachus and Ptolemy joined forces and attacked him. He recalled Demetrius from Greece and moved against Lysimachus. The army of father and son was defeated by the united forces of Seleucus and Lysimachus at Ipsus in 301 BC. Antigonus himself died in the battle after being struck by a javelin. Prior to Ipsus, he had never before had lost a battle. With his death any plans he may have had of reuniting Alexander's Empire came to an end. The victors did not claim power over each other, but instead accepted their kingdoms as separate. Antigonus's kingdom was divided up, with most ending up in the hands of Lysimachus and Seleucus.

Demetrius took control of Macedon in 294 BC, which the family held, off and on, until it was conquered by the Roman Republic at the Battle of Pydna in 168 BC.

References

• Diodorus Siculus xviii., xx. 46-86
• Plutarch, Demetrius, Eumenes
• Nepos, Eumenes
• Justin xv. 1-4
• Köhler, "Das Reich des Antigonos," in the Sitzungsberichte d. Berl. Akad., 1898, p. 835 f.
• This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.