SM U-46, was a Type U 43 submarine launched in 1915 and that served in the First World War until surrendered to Japan on 26 November 1918; later served as Japanese submarine O-2, 1920–21; rebuilt for test purposes in 1925 but lost in storm; hulk scuttled after discovered by U.S. merchant ship in August 1927
During the First World War, Germany also had these submarines with similar names: