SS Glitra was a steam cargo ship that was launched in 1881 as Saxon Prince. In 1896 she was renamed Glitra. In 1914 she became the first British merchant vessel to be sunk by a U-boat in the First World War.

U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. The term is an anglicised version of the German word U-Boot, a shortening of Unterseeboot, though the German term refers to any submarine. Austro-Hungarian Navy submarines were also known as U-boats.