U-23 may refer to one of the following German submarines:
- SM U-23 (Germany), was the lead ship of the Type U 23 class of submarines; launched in 1913 and served in the First World War until sunk on 20 July 1915
- German submarine U-23 (1936), a Type IIB submarine that served in the Second World War until scuttled on 10 September 1944
- German submarine U-23 (S172), a Type 206 submarine of the Bundesmarine that was launched in 1974 and sold after dedommissioning to Columbia were she serves as ARC Intrépido.
U-23 or U-XXIII may also refer to:
|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.|
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