Kallatis was founded by settlers from Herakleia Pontika in the 6th century BCE.
Diogenes Laertius records it as the birthplace of Demetrios of Kallatis, who wrote a geography of Europe and Asia in twenty books (now lost) that is quoted at times by Strabo. He also records a philosopher, Thales of Kallatis with an “affected style.”
Kallatis would have come under the control of Philip II and later Alexander when the former marched against Istros, while was to the north of Kallatis along the coast. After Alexander’s death, Lysimachos took control. He later gave siege to the city after they revolted against him.
That siege was lifted upon word that Antigonos I Monophthalmos had sent two detachments against him, one by land and one by sea. Lysimachos then turned his attentions to the land force, but was met by Seuthes III, who had gone over to Antigonos. Lysimachos defeated him, but not without significant casualties of his own.