The naval operations in the Dardanelles campaign took place against the Ottoman Empire during the First World War. Ships of the Royal Navy, French Marine nationale, Imperial Russian Navy and the Royal Australian Navy, attempted to force the defences of the Dardanelles Straits, a narrow, 41 mi long waterway connecting the Mediterranean Sea with the Black Sea.
The Dardanelles campaign began as a naval operation but the success of the Ottoman defence led the Allies to initiate the Gallipoli campaign, an attempt to occupy the Gallipoli peninsula with land forces supported by the navies, to open the sea route to Constantinople. The Allies also tried to pass submarines through the Dardanelles to attack Ottoman shipping in the Sea of Marmara.