'''Dionysius the Younger''' or '''Dionysius II''' (c. 397 BC – 343 BC) was a Greek politician who ruled Syracuse+, Sicily+ from 367 BC to 357 BC and again from 346 BC to 344 BC.
He was the son of Dionysius the Elder+. When his father died in 367 BC, Dionysius began ruling under the supervision of his uncle, the philosopher Dion+. Dion's disapproval of the young Dionysius's lavishly dissolute lifestyle compelled him to invite his teacher Plato+ to visit Syracuse. Together they attempted to restructure the government to be more moderate, with Dionysius as the archetypal philosopher-king (see the ''Seventh Letter+'' of Plato+).
However, under the influence of opponents of Dion's reforms, Dionysius conspired with the historian Philistus+ and banished his uncle, taking complete power in 366 BC. Without Dion, Dionysius's rule became increasingly unpopular, as he was mostly incompetent in governing men and commanding soldiers. When Plato appealed for Dion's return, the irritated Dionysius interfered with Dion's property and finances and gave his wife to another man. Before this, Dion's Syracusan estates had financed his peaceful and comfortable life overseas in Athens+, but Dionysius's last offence spurred him into action.
Dion formed a small army at Zacynthus+ and returned to Sicily in 357 BC, much to the delight of the Syracusans. As Dionysius was in Caulonia+, Italy+ at the time, Dion easily took all but Syracuse's island citadel. Dionysius sailed back to Syracuse immediately, and upon his return he attempted attacks from the citadel and tried to negotiate peace treaties. When he was unsuccessful in all attempts, he sailed away to Locri+, Italy and left the citadel in the hands of his son Apollocrates+.
In exile, Dionysius took advantage of the friendly citizens of Locri and became the city's tyrant, treating the locals with great cruelty. He did not return to Syracuse until 346 BC, eight years after Dion's assassination by his officers. Soon after he left Locri, the locals drove out the remaining troops and took their revenge wstitle=Dionysius (Tyrant of Syracuse)|display=Dionysius s.v. Dionysius, known as "the Younger"|volume=8|page=284 The people all hooted on Dionysius+
Dionysius also appears in Dante's ''Inferno''+, in which he is referred to as "Dionysius of Sicily" in Canto 12. He is among the many souls named by Chiron that boil in blood for violence against others.
The Renaissance alchemist Michael Maier+ relates a legend about Dionysius II in his book ''Atalanta Fugiens'' (1617), where he was shipwrecked at the Gulf of Corinth+, and without his swimming skills he could have never reached the shore. At Corinth, although he lived poorly, he became a teacher. Maier uses this legend as an allegory to explain a certain point in the Magnum opus+, when the "philosophical subject" (the stone) must ascend to the surface of the "philosophical water".
Dionysius also features in Mary Renault+'s ''The Mask of Apollo''.