In the introduction to his historical treatise the Athenian historian Thucydides mentions the most ancient naval battle in Greek history that took place between the Corinthians and their colonists Corcyraeans around 664 BC, of which battle there is no account in other sources. Having analysed the information on the relationships between Corinth and Corcyra in the Archaic and early Classical periods provided by the written tradition of antiquity, the author of the article arrives at the conclusion that it was but one of many conflicts between the metropolis and its colony, which started as early as the end of the 8th century BC and by the end of the 5th century BC became one of the reasons for the Peloponnesian War that split the ancient Greek world into two camps.