U-5 may refer to one of the following German submarines:
, was the lead boat of the Type U 5 submarines; launched in 1910 and served in the First World War until sunk on 18 December 1914 During the First World War, Germany also had these submarines with similar names: , a Type UB I submarine launched in 1915 and broken up in 1919 , a Type UC I submarine launched in 1915 and grounded on 27 April 1916; the scuttling charges did not go off and the submarine was captured and displayed in London and New York for propaganda purposes , a Type IIA submarine that served in the Second World War and was sunk on 19 March 1943 , a Type 205 submarine of the Bundesmarine that was launched in 1963 and scrapped in 1974
U-5 or U-V may also refer to: , lead boat of the for the Austro-Hungarian Navy