The sinking of the Cunard ocean liner RMS Lusitania occurred on Friday, 7 May 1915 during the First World War, as Germany waged submarine warfare against the United Kingdom which had implemented a naval blockade of Germany. The ship was identified and torpedoed by the German U-boat U-20 and sank in 18 minutes, and also took on a heavy starboard list. The vessel went down 11 miles off the Old Head of Kinsale, Ireland, killing 1,198 and leaving 761 survivors. The sinking turned public opinion in many countries against Germany, contributed to the American entry into World War I and became an iconic symbol in military recruiting campaigns of why the war was being fought.
Lusitania fell victim to torpedo attack relatively early in the First World War, before tactics for evading submarines were properly implemented or understood. The contemporary investigations in both the United Kingdom and the United States into the precise causes of the ship's loss were obstructed by the needs of wartime secrecy and a propaganda campaign to ensure all blame fell upon Germany.