narrow strait in northwestern Turkey

The Bosporus or Bosphorus[1] is a strait that forms part of the boundary between the European part of Turkey and its Asian part (Anatolia). It connects the Black Sea with the Sea of Marmara. It is about 30 km long, with a maximum width of 3,700 metres at the northern entrance, and a minimum width of 700 metres between Kandilli and Aşiyan; and 750 metres between Anadoluhisarı and Rumelihisarı. The depth varies from 36 to 124 metres in midstream.

Satellite image of the Bosporus and Istanbul, taken from the International Space Station in April 2004
View of the Bosporus and Fatih Sultan Mehmet Bridge as seen from Rumelihisarı

The shores of the strait are heavily populated as Istanbul is located on each side. Three bridges and one tunnel cross the strait.


  1. also known as the Istanbul Strait, (Turkish: İstanbul Boğazı) (Greek: Βόσπορος)

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41°07′10″N 29°04′31″E / 41.11944°N 29.07528°E / 41.11944; 29.07528