RMS Atrato was a UK steamship that was built in 1888 as a Royal Mail Ship and ocean liner, became the cruise ship The Viking in 1912 and was converted into the armed merchant cruiser HMS Viknor in 1914. She sank in 1915 with all hands, a total of 295 Royal Navy officers and men.
When the UK entered the First World War in 1914 the Admiralty requisitioned her, had her re-fitted as an armed merchant cruiser and commissioned her as HMS Viknor. She was placed under the command of Commander EO Ballantyne with a complement of 22 officers and 273 ratings and assigned to the 10th Cruiser Squadron.
On 28 December 1914 Viknor went on patrol from the River Tyne. On 13 January 1915 she sank with all hands in heavy seas off Tory Island, County Donegal, Ireland. She sent no distress signal. Some wreckage and many corpses washed ashore on the Irish coast.
It is thought she struck a German naval mine, possibly one of those laid by the German Bremen-class cruiser SMS Berlin. Her wreck was found in 2006, and in 2011 a scuba diver placed a White Ensign on it in memory of her complement.[6]