'Knife' (i) was a British unsuccessful submarine operation to land officers and stores at Ålesund on the west coast of Norway (26/27 April 1940).

As a replacement for the damaged submarine Truant, Clyde departed Rosyth on this mission, which was intended to strengthen British capabilities in the aftermath of the 'Weserübung' invasion of Norway by the Germans, but then developed engine problems and had to turn back.