The conspiracy of Cinadon was an attempted coup d'état which took place in Sparta in the 4th century BC during the first years of the reign of Eurypontid King Agesilaus II (398 BC-358 BC). The leader was Cinadon, who was a distinguished military officer, but came from a poor family. The conspiracy aimed to break the power of the oligarchic Spartan state and its elite and give rights to poorer Spartans and even to helots. Although elaborately organized, the plot was in the end betrayed to the ephors; they cracked down on the conspirators, and Cinadon himself was tortured and executed.
Cinadon's conspiracy can be seen as a predecessor to many other radical movements of the ancient world, such as the Catiline Conspiracy in Rome or even the slave revolt of Spartacus.
Cinadon was a young and valiant man. He was a military officer who carried out important missions for the ephors; he had a scytale in his possession which was used to direct Hippeis, members of the elite Spartan guard of the Spartan army. He was well educated and, because of his job, he should have been a valued and respected person likely (according to Xenophon and Aristotle) to be a member of the peers (Homoioi). In fact, he was a member of the "Inferiors" (hypomeiones), those Spartans who had lost their civil rights either through cowardice, or poverty (for example, the inability to pay their dues to the syssitia), as was the case for Cinadon, who had a humble background. He aspired, as he stated in the course of his trial, "to be a Lacedaemonian inferior to no one".
He assembled other hypomeiones, of whom the most dangerous, according to Xenophon, was the seer Tisamenus, a descendant of an Elean of the same name who had received Spartan citizenship after the Greco-Persian Wars. He had also lost his civil rights, probably because of poverty. These two plotters were not members of the oppressed classes, but had been stripped of their usual rights as citizens.