SM UC-56
 SM UC-56 was a German Type UC II minelaying submarine or U-boat in the German Imperial Navy (German: Kaiserliche Marine) during World War I. The U-boat was ordered on 12 January 1916 laid down on 4 March 1916 and was launched on 26 August 1916. She was commissioned into the German Imperial Navy on 18 December 1916 as SM UC-56. In 6 patrols UC-56 was credited with sinking 1 ship by torpedo: the British hospital ship Glenart Castle.