a Spartan tyrant, usurped the supreme power in Lacedemon on the death of Machanidas, at the battle of Mantinea, in 207 B.C. His government was established on a system of unbridled cruelty and rapacity. The most influential citizens were put to death or were driven into exile; temples were plundered; and the wealthy were subjected to exorbitant taxes. If they refused to pay, they were summoned before the tyrant. If their obstinacy still continued, a new engine of torture, made in the form of a woman, and having its breast and arms bristling with spikes, was forthwith produced. "Perhaps," said Nabis, "my wife Apega will be able to persuade you." They were then subjected to the horrid embrace of this automaton, and were tortured into compliance. With the money extorted in this manner the tyrant hired the services of all the vagabonds, ruffians, and cut-throats of the country. Some of these were sent to prowl and plunder throughout all parts of the Peloponnesus; others were employed to dog the footsteps of any dangerous Spartan exile, and to murder him as he fled along the way, or sat in fancied security in some friendly city; the rest were organized into a formidable mercenary army for the support and extension of the tyrant's power.

After this ruthless despotism had awed Sparta into submission, Nabis began to turn his thoughts to foreign conquest. His great project was to regain the Lacedaemonian ascendancy in the Peloponnesus. He began his attempt by invading the territories of Megalopolis, and by then seizing upon Messene. The skilful strategy of Philopoemen, the leader of the forces of the Achaean League, drove him back within his own domains in 201 B.C.; yet in the following year his army was again in the field, and was laying close siege to Megalopolis. About the same time he was pretending to favour the cause of Philip of Macedon against the Romans, that he might obtain possession of Argos. In 198 B.C. he attained his object, and then immediately struck a treaty with the Roman general Flamininus. This deceitful time-serving, however, did not prepossess his new allies in his favour, and they seized the earliest opportunity to break the truce. In 195 B.C., the year after peace had been concluded between Rome and Philip of Macedon, Nabis received intelligence that Flamininus was marching against him. The most decisive measures for resistance were forthwith taken. To secure the fidelity of his troops, eighty suspected persons were put to death for the sake of example. The defences of Sparta were greatly strengthened; yet after the Lacedaemonians had been twice defeated under their own walls, their capital was forced to capitulate. A treaty was ratified, which deprived Nabis of the fruits of his deceit and aggression, and imposed upon him other severe penalties. The Romans, however, had not long departed from Greece when Nabis broke the truce, and marching southward, laid siege to Gythium. A fleet under Philopoemen, the general of the Achaean League, attempted to relieve the town. With a few ships, hastily collected, he completely frustrated the attempt, and compelled the enemy to retreat. The town was soon afterwards taken. Then hastening northward by forced marches, he succeeded in surprising Philopoemen, who was advancing upon Sparta. But the able Achaean general, instantaneously retrieving the surprise, outwitted his foe in return, cut his army to pieces, and ravaged the country composed during the ensuing month. For some time Nabis lay at Sparta, too weak to take the field again. At length, in 192 B.C., he received some Eleans as a pretended reinforcement. They had come, however, in reality to effect his ruin; and he was assassinated by their leader Alexamenus. The ultimate consequences of his death were, that the Eleans were massacred in their turn, and Sparta joined the Achaean League.