Dionysius (Ancient Greek: Διονύσιος, romanized: Dionysios) was a tyrant of Heraclea Pontica on the Euxine (the Black Sea).
After the destruction of the Persian empire by Alexander the Great, Dionysius attempted to extend his dominions in Anatolia.
But, despite these efforts, Dionysius still did not appear to have felt very safe in his position, as evidenced by the delight with which he received the news of Alexander's death.
In 306 BC, when the surviving generals of Alexander assumed the titles of king (basileus), Dionysius followed their example, but he died soon after.
Coins of Dionysius have been found, some of which were issued during his joint reign with his older brother Timotheus and others during his sole rule.