U-38 may refer to one of the following German submarines:
- SM U-38, was a Type U 31 submarine launched in 1914 and that served in the First World War until surrendered on 23 February 1919
- During the First World War, Germany also had these submarines with similar names:
- SM UB-38, a Type UB II submarine launched in 1916 and sunk on 8 February 1918; in 2008 UB-38's wreck was moved to reduce the danger to shipping
- SM UC-38, a Type UC II submarine launched in 1916 and sunk 14 December 1917
- During the First World War, Germany also had these submarines with similar names:
- German submarine U-38 (1938), a Type IX submarine that served in the Second World War until scuttled on 5 May 1945
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.