Aratus of Sicyon (Ancient Greek: Ἄρατος ὁ Σικυώνιος; 271–213 BC) was a politician and military commander of Hellenistic Greece.

When the Spartan king Cleomenes III conquered the Achaean cities of Argos and Corinth, Aratus succeeded in securing an alliance with his erstwhile enemy, Macedon.

The seven-year-old Aratus escaped the coup with the help of his aunt[N 1] who, in the confusion, was able to hide the boy until nightfall and then smuggle him out of Sicyon to Argos.

[5] In 251 BC, Aratus had originally intended to take and hold a fortified post near Sicyon from which he could raid his enemies' property, and where sympathisers could join him.

Plutarch reports that one of the two kings Aratus had earlier petitioned for support gave him 25 talents of silver as a personal gift and goodwill gesture.

Back in Sicyon, Aratus did not want sole responsibility for distributing the money, and established a committee which included himself and fifteen other members for the task.

In 243 BC, Aratus learned from Syrian mercenaries that there was a less steep access route to the hill, where the wall was also at its lowest point.

Weather conditions proved favourable for Aratus:[15] (…) the light of the full moon also made their arms appear more numerous to the enemy than they really were, owing to the length of their line of march, and the echoes of the night gave the impression that the shouts proceeded from many times the number there really were.Aratus' soldiers scaled the walls of the citadel and the garrison surrendered.

But Aratus wanted to avoid immediate fighting, on the grounds that the Aetolians could only cause limited damage at that time as crops had already been harvested and stored.

The front line could no longer be held, allowing the Aetolians to invade the Peloponnese and capture Pellene, one of the first members of the Achaean League.

Aratus reached the city with his army afterwards, but to no avail, and when the Argives sued him for breaking the peace he was convicted by a Peloponnesian court of arbitration in Mantineia.

The Achaeans routed the enemy left flank, but Aratus, leading the other wing under the walls, retreated to the outrage of his officers, allowing Aristippus to claim victory.

The next day, after forming up his army for battle, Aratus noticed that the enemy had gained numerical superiority through reinforcements and ordered withdrawal.

That year, on becoming aware of Aratus' expansionist plans in the Peloponnese; the death of Aristippus; and events in Sparta, Lydiades decided to give up his power by joining the Achaean League.

[23] The Achaean League became a significant power through the efforts of Aratus; a mighty confederation with an organised army financed by tax revenue, controlling all of the northern Peloponnese.

[21] Realising that the Achaean League had become a major player in Greece with the incorporation of Megalopolis, Demetrius II, the new king of Macedon, decided to take action.

Aratus apparently succeeded in escaping the battlefield and reaching Corinth, but reports began to spread that he had been killed or taken prisoner.

Plutarch's tendency to exaggerate notwithstanding, it seems true that the Athenians had no great liking for Aratus despite his wish to liberate the city from Macedonian rule.

[25] While this information is contradictory and cannot be entirely correct,[23] the outcome was the same: Aratus organised a punitive expedition into Attica, but turned back before reaching the walls of Athens.

[26] Aristomachus of Argos, Macedon's only remaining ally in the Peloponnese, bowed to force majeure and finally joined the Achaean League.

Aratus, again strategos, tried to organise nightly attacks to regain control of Tegea and Orchomenus, but was betrayed by his partisans in both cities, who told Cleomenes of the plan.

He marched to Corinth, arriving to face an angry mob: the population had heard of his intention to surrender the city and its citadel to Antigonus.

When Cleomenes heard of the Macedonian intervention, he abandoned the siege of Sicyon as fast as possible, moving to the Isthmus of Corinth, a better position from which to meet the northern threat.

For he knew that his own rise to power had been a consequence of the harm he had done to them, and that he had found the first and the chief basis for his conduct of affairs in his hatred towards the former Antigonus [Gonatas].

But seeing how inexorable was the necessity laid upon him in the demands of the hour, to which those we call rulers are slaves, he went on towards the dread ordeal.Both hard-headed realists, Aratus and Antigonus got along well despite their wariness.

Aratus sailed to Epidaurus with 1,500 troops to attack Argos, but found that it had fallen already to an internal uprising with the help of Timoxenos, then strategos of the Achaean League.

Plutarch reports that Aratus was a great politician, but that his capacities did not extend to the battlefield, saying: "the general of the Achaeans always had cramps in the bowels when a battle was imminent".

[7] Aratus became the most important person within the Achaean League, but it grew progressively more difficult for him to get his way as a succession of other mighty city-states joined.

[29] Although it is unlikely that Aratus was poisoned, his death was certainly linked with the final stage of Philip's transition from beloved young prince to what Plutarch described as an impious despot richly deserving of downfall.

The information concerning Aratus is therefore to be read through a critical filter, allowing for the possibility that he may have wanted to attenuate his own mistakes by blaming others, or that he glorified his own victories.