The affairs of the Sicilian Greeks, an important branch of the Hellenic race, deserve a passing notice. A few years after the destruction of the Athenian armament, Dionysius made himself master of Syracuse, and openly seized upon the supreme power (B.C. 405). His reign as tyrant or despot was long and prosperous. After conquering the Carthaginians, who more than once invaded Sicily, he extended his dominion over a great part of the island, and over a considerable portion of Magna Graecia. He raised Syracuse to be one of the chief Grecian states, second in influence, if indeed second, to Sparta alone. Under his sway Syracuse was strengthened and embellished with new fortifications, docks, arsenals, and other public buildings, and became superior even to Athens in extent and population.

Dionysius was a warm patron of literature, and was anxious to gain distinction by his literary compositions. In the midst of his political and military cares he devoted himself assiduously to poetry, and not only caused his poems to be publicly recited at the Olympic games, but repeatedly contended for the prize of tragedy at Athens. In accordance with the same spirit we find him seeking the society of men distinguished in literature and philosophy. Plato, who visited Sicily about the year 389 from a curiosity to see Mount AEtna, was introduced to Dionysius by Dion. The high moral tone of Plato's conversation did not however prove so attractive to Dionysius as it had done to Dion; and the philosopher was not only dismissed with aversion and dislike, but even, it seems through the machinations of Dionysius, seized, bound, and sold for a slave in the island of AEgina. He was, however, repurchased by Anniceris of Cyrene, and sent back to Athens.

Dionysius died in B.C. 367, and was succeeded by his eldest son, commonly called the younger Dionysius, who was about 25 years of age at the time of his father's death. At first he listened to the counsels of Dion, who had always enjoyed the respect and confidence of his father. At the advice of Dion he invited Plato to Syracuse, where the philosopher was received with the greatest honour. His illustrious pupil immediately began to take lessons in geometry; superfluous dishes disappeared from the royal table; and Dionysius even betrayed some symptoms of a wish to mitigate the former rigours of the despotism. But now the old courtiers took the alarm. It was whispered to Dionysius that the whole was a deep-laid scheme on the part of Dion for the purpose of effecting a revolution and placing his own nephews on the throne. [The elder Dionysius had married two wives at the same time: one of these was a Locrian woman named Doris; the other, Aristomache, was a Syracusan, and the sister of Dion. The younger Dionysius was his elder son by Doris; but he also had children by Aristomache.] These accusations had the desired effect on the mind of Dionysius, who shortly afterwards expelled Dion from Sicily. Plato with difficulty obtained permission to return to Greece (B.C. 366). Dionysius now gave way to his vices without restraint, and became an object of contempt to the Syracusans. Dion saw that the time had come for avenging his own wrongs as well as those of his country. Collecting a small force, he sailed to Sicily, and suddenly appeared before the gates of Syracuse during the absence of Dionysius on an expedition to the coasts of Italy. The inhabitants, filled with joy, welcomed Dion as their deliverer: and Dionysius on his return from Italy found himself compelled to quit Syracuse (B.C. 356), leaving Dion undisputed master of the city. The latter was now in a condition to carry out all those exalted notions of political life which he had sought to instil into the mind of Dionysius. He seems to have contemplated some political changes; but his immediate and practical acts were tyrannical, and were rendered still more unpopular by his overbearing manners. His unpopularity continued to increase, till at length one of his bosom friends - the Athenian Callippus - seized the opportunity to mount to power by his murder, and caused him to be assassinated in his own house. This event took place in 353, about three years after the expulsion of the Dionysian dynasty. Callippus contrived to retain the sovereign power only a twelvemonth. A period of anarchy followed, during which Dionysius made himself master of the city by treachery, about B.C. 346. Dionysius, however, was not able to re-establish himself firmly in his former power. Most of the other cities of Sicily had shaken off the yoke of Syracuse, and were governed by petty despots. Meantime the Carthaginians prepared to take advantage of the distracted condition of Sicily. In the extremity of their sufferings, several of the Syracusan exiles appealed for aid to Corinth, their mother-city. The application was granted, and Timoleon was appointed to command an expedition destined for the relief of Syracuse.