Dionysius was a tyrant of Heraclea on the Euxine. He was a son of Clearchus, who had assumed the tyranny in his native place. When Clearchus died, he was first succeeded by his brother Satyrus, who was reigning as guardian for Clearchus' sons Timotheus and Dionysius. Satyrus was succeeded by Timotheus, who soon shared the power with his younger brother Dionysius. After the death of the Timotheus, Dionysius became the sole ruler of Heraclea. After the destruction of the Persian empire by Alexander the Great, Dionysius attempted to extend his dominions in Anatolia. In the meantime, some of the citizens of Heraclea, who had been driven into exile by their tyrants, applied to Alexander to restore the republican government at Heraclea, but Dionysius, with the assistance of Alexander's sister, Cleopatra of Macedon, contrived to prevent any steps being taken to that effect. But still he does not appear to have felt very safe in his position, as we may conjecture from the extreme delight with which he received the news of Alexander's death, in consequence of which he erected a statue of euthymia, that is, joy or peace of mind. The exiled Heracleans now applied to Perdiccas, against whom Dionysius endeavoured to secure himself by joining his enemies. Dionysius therefore married Amastris, the former wife of Craterus, who secured to him considerable advantages. A friendship with Antigonus was formed by assisting him in his war against Asander, and Ptolemy, the nephew of Antigonus, married Dionysius' daughter by his first wife. Dionysius thus remained in the undisturbed possession of the tyranny for many years. In 306 BC, when the surviving generals of Alexander assumed the title of kings, Dionysius followed their example, but he died soon after. He was an unusually fat man, which increased at length to such a degree that he could take no food, which was therefore introduced into his stomach by artificial means. At last, however, he was choked by his own fat. He is said to have been the mildest and justest of all the tyrants that had ever lived. He was succeeded by his wife Amastris, who reigned during the minority of her sons Clearchus II and Oxyathres. The death of Dionysius must have taken place in 306 or 305 BC, as, according to Diodorus, he died at the age of 55, and after a reign of 32 years, for which others say 33 years. There have been found coins of Dionysius, some of which were issued during his joint reign with his older brother Timotheus and others during his sole rule.