Dion Of Syracuse, a disciple of Plato, celebrated for having overthrown the power of Dionysius the Younger, tyrant of Syracuse, born in that city toward the close of the 5th century B. C, killed in 354 or 353. Under Dionysius the Elder, to whom he was doubly related by marriage, he enjoyed the favor of the court, and amassed great wealth; but when the younger Dionysius succeeded to the throne (367), Dion, whose austere manners were a constant rebuke of the royal debaucheries, fell into disfavor, and at last was banished from Sicily. He found refuge and a friendly reception in Greece, where he lived for a while in affluence, his income being allowed to reach him. Soon, however, this was cut off, and to complete his disgrace his wife Arete was compelled to marry another man. Dion now resolved to avenge himself and his country at the same time. Having assembled about 800 troops, he sailed from Zacynthus (357), landed in Sicily, and easily obtained possession of Syracuse in the absence of Dionysius. The troops of the tyrant still held the citadel on the neighboring island of Ortygia, whence they made a sally soon after the arrival of Dion, and were repulsed only after a fierce combat, during which Dion himself displayed great courage.

He was at first received by the citizens with enthusiasm, and on his entry into the city he proclaimed liberty to Syracuse. But, irritated by his harsh manners, suspecting his designs, and incited by the demagogue Heraclides, the people afterward expelled him and his troops. The Syracusans soon had reason to repent of their conduct, for the soldiers of Dionysius, aware of their dissensions, made a sally, regained part of the city, set fire to the houses, and began a fearful massacre. The banished philosopher was entreated to return, and, marching immediately, after a hard contest he obtained full control of Syracuse. He caused Heraclides to be put to death. This act greatly injured his popularity, already damaged by his repellent and austere manners; a conspiracy was formed against him, and he was assassinated.