German submarine U-56

U-56 may refer to one of the following German submarines:


 * SMU U-56, a Type U 51 submarine launched in 1916 and that served in the First World War until she went missing after 3 November 1916
 * During the First World War, Germany also had these submarines with similar names:
 * SMU UB-56, a Type UB III submarine launched in 1917 and sunk on 19 December 1917
 * SMU UC-56, a Type UC II submarine launched in 1916 and interned at Santander, Spain, on 24 May 1918. UC-56 sank the British hospital ship HMHS Glenart Castle on 26 February 1918.
 * GS U-56 (1938), a Type IIC submarine that served in the Second World War until sunk 28 April 1945