HMHS Gloucester Castle (His Majesty's Hospital Ship) was a steam ship originally built for the Union-Castle Line, but requisitioned for use as a British hospital ship during the First World War. On 31 March 1917 she was torpedoed by German U-boat UB-32. She was, however, salvaged, and returned to civilian service after the war. She was sunk by the German commerce raider Michel in 1942 off Ascension Island in the South Atlantic.