U-2 may refer to one of the following German submarines:

• SM U-2 (Germany), a unique submarine launched in 1908 that served in the First World War as a training submarine and was scrapped in 1919
  • During the First World War, Germany also had these submarines with similar names:
    • SM UB-2, a Type UB I submarine launched in 1915 and scrapped in 1919
    • SM UC-2, a Type UC I submarine launched in 1915 and sunk on 30 June 1915
• German submarine U-2 (1935), a Type IIA submarine that served in the Second World War and was sunk on 8 April 1944
• German submarine U-2 (1962), a Type 201 submarine of the Bundesmarine, launched in 1962
• German submarine U-2 (1966), a Type 205 submarine of the Bundesmarine that was launched in 1966 and sold in 1993

U-2 or U-II may also refer to:

• SM U-2 (Austria-Hungary), a U-1-class Austro-Hungarian Navy submarine

List of ships with the same or similar names

This article includes a list of ships with the same or similar names. If an internal link for a specific ship led you here, you may wish to change the link to point directly to the intended ship article, if one exists.