U-77 may refer to one of the following German submarines:
- SM U-77, a Type UE I submarine launched in 1916 and that served in World War I until sunk 7 July 1916
- During World War I, Germany also had these submarines with similar names:
- SM UB-77, a Type UB III submarine launched in 1917 and surrendered on 16 January 1919; broken up at Swansea in 1922
- SM UC-77, a Type UC II submarine launched in 1916 and sunk on 14 July 1918
- During World War I, Germany also had these submarines with similar names:
- German submarine U-77, a Type VIIC submarine that served in World War II until sunk on 28 March 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.