U-135 may refer to one of the following German submarines:
- SM U-135, a Type U 127 submarine launched in 1917 and that served in the First World War until surrendered on 20 November 1918; grounded on east coast of England on way to be broken up in 1921
- During the First World War, Germany also had this submarine with a similar name:
- SM UB-135, a Type UB III submarine ordered in 1917 but not completed by the end of the war
- During the First World War, Germany also had this submarine with a similar name:
- German submarine U-135 (1941), a Type VIIC submarine that served in the Second World War until sunk 15 July 1943
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.