Bosphorus strait is a natural strait located in northwestern Turkey, connecting the Black Sea to the Sea of Marmara. In ancient times, the Black Sea had no outlet, and its water level was lower than the Aegean and the Marmara Sea.

Also known as the Strait of Istanbul, it links the European part of the city with its Asian part and thus remains a strategic waterway in the region. The Bosphorus strait has played a significant role in world maritime trade for centuries.