RMS Lusitania was an ocean liner operated by the Cunard Company that served the Liverpool, England – New York City, United States route on the North Atlantic. The ship was designed by Leonard Peskett and built by John Brown and Company of Clydebank, Scotland. The ship was named after the ancient Roman province of Lusitania, which is now part of present-day Portugal and western Spain.

• Operator: Cunard Line, Ltd.
• Builder: John Brown and Co., Clydebank, Scotland
• Keel laid: 16 June 1904
• Launched: 7 June 1906
• Maiden voyage: Liverpool, England – New York, USA, 7 – 13 September 1907
• Round trip voyages: 101 (202 crossings)
• Length of career: 7 yrs, 9 months

Lusitania was launched on 7 June 1906 and entered service for Cunard on 26 August 1907. When she entered service, Lusitania set the records for the largest and fastest ship afloat, taking these records from the ships of the United Kingdom’s naval rival, Germany. Lusitania maintained these records until the entry of her twin sister Mauretania into the North Atlantic run. Lusitania, Mauretania, and slower but larger Aquitania provided a weekly passenger service for the Cunard Line just prior to the First World War.

During World War I, Germany waged submarine warfare against the United Kingdom. Lusitania, which had been built with the capability of being converted into a warship, was identified as a target. The German submarine U-20 torpedoed and sank her on 7 May 1915; this was early in the war before tactics for evading submarines were fully developed. The ship suffered two explosions, the second one which could never fully be explained, and sank in 18 minutes. The Lusitania disaster killed 1,192 of the 1,960 known people on board, leaving 768 survivors. Four of these survivors died soon afterwards of trauma sustained from the sinking, bringing the final death toll to 1,196.

The sinking turned public opinion against Germany, particularly those in Ireland and the then-neutral United States.