Which strait separates the European and Asian parts of Istanbul?

The Bosphorus separates the European and Asian parts of Istanbul.

The Bosphorus is a narrow natural strait connecting the Black Sea to the Sea of Marmara. Istanbul occupies both shores, making it one of the world’s most prominent transcontinental cities. The waterway is approximately 31 kilometres long, although its width varies considerably.

The strait has been strategically important for thousands of years because ships traveling between the Black Sea and the Mediterranean must pass through it and the Dardanelles. Ancient Greek Byzantium and later Constantinople grew beside this crossing. In 1936, the Montreux Convention established rules governing passage by warships and merchant vessels.

The Bosphorus is often confused with the Dardanelles, which lies farther southwest and connects the Sea of Marmara to the Aegean Sea. Together, the Bosphorus, Sea of Marmara and Dardanelles form the Turkish Straits system.