German submarine U-27

U-27 may refer to one of the following German submarines:


 * SMU U-27 (Germany), was the lead ship of the Type U 27 class of submarines; launched in 1913 and served in the First World War until sunk on 19 August 1915; the events surrounding U-27's sinking are known as the Baralong Incident
 * During the First World War, Germany also had these submarines with similar names:
 * SMU UB-27, a Type UB II submarine launched in 1915 and sunk on 27 July 1917
 * SMU UC-27, a Type UC II submarine launched in 1916 and surrendered on 3 February 1919
 * GS U-27 (1936), a Type VIIA submarine that served in the Second World War until sunk on 20 September 1939
 * GS U-27 (S176), a Type 206 submarine of the Bundesmarine that was launched in 1974 and scrapped in 1996

U-27 or U-XXVII may also refer to:
 * SMU U-27 (Austria-Hungary), lead boat of the U-27 class submarines for the Austro-Hungarian Navy