SM U-15 was one of the three Type U 13 gasoline-powered U-boats produced by the German Empire for the Imperial German Navy. On 9 August 1914, U-15 became the first U-boat lost to an enemy warship after it was rammed by British light cruiser in the North Sea.
Constructed by Kaiserliche Werft Danzig, U-15 was ordered on 23 February 1909 and commissioned three years later on 7 July 1912. At the start of World War I the boat was commanded by Kapitänleutnant Richard Pohle. The boat left port for its first patrol on 1 August 1914, part of a group of U-boats tasked with attacking the British naval base at Scapa Flow.
On 9 August, U-15 was forced to lie stopped on the surface off the coast of Fair Isle, in Shetland, after its engines failed. Whilst it was stranded on the surface in thick fog, the British cruiser HMS Birmingham was alerted to the boat after hearing hammering, presumed to be an attempt to repair U-15s engines. Birminghams Captain Arthur Duff ordered his crew to fire on the U-boat, but missed. As U-15 attempted to dive to avoid the attack, Duff ordered his ship to ram the submarine at full speed, cutting it in half and sinking it at . All 25 members of the submarine's crew were killed.