RMS Alcantara was an ocean liner which entered service just weeks before the start of World War I, was converted to an armed merchant cruiser in 1915, and was sunk in combat with the German armed merchant cruiser SMS Greif in the Action of 29 February 1916.

[3] Alcantara was launched on 30 October 1913 and made her maiden voyage in June 1914 on RMSP's route from Southampton to Rio de Janeiro, Montevideo and Buenos Aires.

[4] In April 1915 the British Admiralty requisitioned Alcantara and her "A-series" sisters Avon, Arlanza and Andes to be armed merchant cruisers.

On 17 April at Liverpool she was commissioned into the Royal Navy's 10th Cruiser Squadron as HMS Alcantara, with the pennant number M 94.

[6] Arlanza and Andes were also commissioned into the 10th Cruiser Squadron, which joined the Northern Patrol that was part of the First World War Allied naval blockade of the Central Powers.

[6] It found no evidence of enemy activity; only the remains of the Austro-Hungarian North Pole Expedition base built in 1882 and three Arctic fox cubs, which for a short time were taken aboard as pets.

[7] She was due to return to port on 1 March, but on the morning of 29 February 1916 she was northeast of Shetland en route to a rendezvous with Andes she intercepted the Imperial German Navy merchant raider Greif disguised as the Norwegian merchant ship Rena with a home port of Tønsberg, Norway.

[1] However, Alcantara's commanding officer, Captain Thomas Wardle, reported that after lowering the Norwegian ensign Greif fought under no flag.

The first shell hit Alcantara's bridge, disabling her steering gear, engine order telegraph and all telephones and killing or wounding a number of men.

Several of Alcantara's lifeboat falls had been damaged by enemy fire, so that attempts to launch some boats caused men to be dropped into the sea.