The Propontide ( " propontis" , " Προποντίς" , " - ίδος" ) is the name under which the ancient Greeks indicated the Marmara Sea, between the Aegean Sea and the Black Sea. Its etymology derives from the terms pro (before) and pontos (sea) because it allowed for the Greek old to reach the Euxine Sea (current the Black Sea).

The principal cities of Propontide were Byzance and Chalcédoine, with the mouth of the the Bosphorus. The areas bathed by this sea were, side Asiatique, the Mysie with the Southern and the Bithynie with the Northern , and the Thrace side Européen.