Cleomenes III was the son of Leonidas II. He became King of Sparta in 235 BC.

He continued the reforms of Agis IV. Less squeamish than his predecessor, in 227 BC the opposition in Sparta were removed in a coup - four of the five ephors were killed and eighty opponents were exiled. He deposed his colleague Archidamus V and installed his brother Eucleidas as co-ruler. The Achaean general Aratus was checked in a series of rapid and bold campaigns. The land was redistributed into 4,000 lots and perioikoi and hypomeinones were allowed to participate. The army was reorganized on the Macedonian model and a small subsidy from Ptolemy III Euergetes was paid.

This social revolution provided Cleomenes with both the means to restore Spartan greatness, a general support in the rest of the Peloponnese and the reason for its eventual failure. A united Peloponnese under a reformed and revitalised Sparta could have been a power in the Hellenistic world and a challenge to Macedonia.

In 226 BC the new army continued to have success. Most of Arcadia, Corinth, Argos and the Argolid succumbed to him or joined him and the Achaeans were routed at the Battle of Dyme. The Achaeans under Aratus who had once cleared the Peloponnese of the Macedonians now appealed to Antigonus III Doson of Macedon with Corinth as the price. Ptolemy III Euergetes now stood aside and stopped the subsidy, and Sparta stood alone. Inevitable it may have been but a Macedonian victory would not be simple. In 224 BC Cleomenes fortified the isthmus but his position was turned with the defection of Argos. Much of Arcadia was lost in 223 but Megalopolis was destroyed by Cleomenes. Short of money and men Cleomenes sold 6,000 helots their freedom and hired more mercenaries.

For his last campaign in 222 BC he faced 28,000 Macedonians with 10,000 Spartans at the Battle of Sellasia on the road to Tegea, but despite a well chosen position and skillful handling the Spartans were overwhelmed. Plutarch says that of the 6,000 Lacedaemonians present only 200 survived. Cleomenes was deposed and was killed in exile in 219 BC.

Succeeded by: Agesipolis III

Plutarch's Lives of the Noble Greeks and Romans Alcibiades and Coriolanus - Alexander the Great and Julius Caesar - Aratus & Artaxerxes and Galba & Otho Aristides and Cato the Elder - Crassus and Nicias - Demetrius and Antony - Demosthenes and Cicero Dion and Brutus - Fabius and Pericles - Lucullus and Cimon - Lysander and Sulla - Numa and Lycurgus Pelopidas and Marcellus - Philopoemen and Flamininus - Phocion and Cato the Younger - Pompey and Agesilaus Poplicola and Solon - Pyrrhus and Gaius Marius - Romulus and Theseus - Sertorius and Eumenes Tiberius Gracchus & Gaius Gracchus and Agis & Cleomenes - Timoleon and Aemilius Paulus - Themistocles and Camillus