The Bosporus separates Europe from Asia in Istanbul and connects the Black Sea with the Sea of Marmara. The strait runs through Turkey’s largest city, placing Istanbul on two continents and making the waterway one of the world’s most recognizable geographic boundaries.
The Bosporus is about 30 kilometres long, though its width varies considerably. At its narrowest, it is only around 700 to 750 metres wide. Strong currents, sharp bends, and dense urban development make navigation challenging, yet it remains an important international shipping route.
Together with the Dardanelles and the Sea of Marmara, the Bosporus forms part of the Turkish Straits. This chain of waterways provides the maritime route from the Black Sea to the Aegean and Mediterranean seas. Its strategic position has influenced the history of Byzantium, Constantinople, the Ottoman Empire, Russia, and the modern states bordering the Black Sea.
The Dardanelles is the common mix-up. It is also part of the Turkish Straits, but it lies southwest of the Sea of Marmara and connects that sea with the Aegean. The Bosporus is the section running through Istanbul.