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Bosporus.org covers the Bosporus, the narrow strait that runs through Istanbul and joins the Black Sea to the Sea of Marmara. It is about 31 kilometres long and under 700 metres wide at its narrowest, and it carries tens of thousands of ships a year past apartment blocks, palaces and fishing piers. Few waterways matter so much to so many countries while running through the middle of a city of more than 15 million people.

We follow the strait on three lines. Shipping: the tankers, bulk carriers and container ships that pass through, the rules for pilots and transit, the grain and oil trades, and projects like Canal Istanbul. Security: the 1936 Montreux Convention, which still decides which warships may pass, Turkey's role as the strait's keeper, and what the war in Ukraine has done to the Black Sea. And Istanbul: the waterside neighbourhoods, fortresses, palaces, bridges and ferries on both the European and Asian shores.

The name is spelled two ways in English. Bosporus is the scholarly spelling used by most reference works and atlases; Bosphorus, the variant in the Montreux Convention's own text, is common in travel writing and in Turkey's own English. Turks call it İstanbul Boğazı, the Istanbul Strait. All three mean the same water.

We read official sources, shipping data and Turkish and international reporting, check them against each other and date anything that changes.

Bosporus.org is an independent site. It has no affiliation with the Republic of Türkiye, the Istanbul Metropolitan Municipality or any authority that manages the strait.