The Battle of Río de Oro was a single-ship action fought in August 1914 during the First World War, when HMS Highflyer attacked the German SS Kaiser Wilhelm der Grosse off Río de Oro on the coast of Northwest Africa.

Under the command of Max Reymann, Imperial German Navy ship SS Kaiser Wilhelm der Grosse was originally a passenger liner, built in 1897, part of the German merchant fleet until requisitioned for service at the outbreak of World War I and fitted with six 4-inch guns and two 37-millimeter guns.

Eventually, Kaiser Wilhelm der Grosse exhausted her ammunition and sought to flee the battle.

Kaiser Wilhelm der Grosse became the first passenger liner to sink during World War I.

The wreck of the German commerce raider was identifiable because its starboard side remained above the waterline until the ship was scrapped in 1952.