RMS Lusitania was a British-registered ocean liner that was torpedoed by an Imperial German Navy U-boat during the First World War on 7 May 1915, about 11 nautical miles (20 km; 13 mi) off the Old Head of Kinsale, Ireland (then part of the United Kingdom). The attack took place in the declared maritime war-zone around the United Kingdom, three months after unrestricted submarine warfare against the ships of the United Kingdom had been announced by Germany following the Allied powers' implementation of a naval blockade against it and the other Central Powers.
The passengers had been notified before departing New York of the general danger of voyaging into the area in a British ship, but the attack itself came without warning.