The Bosphorus or Bosporus (; , Bósporos; ) is a natural strait and internationally-significant waterway located in northwestern Turkey that forms part of the continental boundary between Europe and Asia, and separates Asian Turkey from European Turkey. The world's narrowest strait used for international navigation, the Bosporus connects the Black Sea with the Sea of Marmara, and, by extension via the Dardanelles, the Aegean and  Mediterranean Seas.