'SK' was a British abortive naval undertaking by Admiral Sir Charles Forbes’s Home Fleet to attack German shipping off the coast of Norway (22/23 September 1939).

The undertaking was centred on the light cruisers of the 2^nd Cruiser Squadron (Southampton and Glasgow) and 18^th Cruiser Squadron (Aurora and Sheffield) and a force of eight destroyers of the 6^th Destroyer Flotilla (Bedouin, Eskimo, Punjabi and Tartar) and 7^th Destroyer Flotilla (Javelin, Jersey, Jervis and Jupiter), which were to penetrate deep into the Skagerrak with the object of drawing out German heavy warships and leading them toward the Home Fleet covering force. Secondary objectives were to investigate reports that a boom had been laid across the entrance to the Kattegat, to sink any German ships encountered, and to exercise contraband control.

The main weight of the British attack was vested in the battleships Nelson and Rodney, the battle-cruisers Hood and Repulse, the fleet carrier Ark Royal and the destroyers Fame, Faulknor, Fearless, Firedrake, Foresight, Fortune, Foxhound, Mashona, Matabele and Somali, which sortied from Scapa Flow in the Orkney islands group at 11.00 on 22 September, but following a collision between the destroyers Javelin and Jersey of the cruiser force, the whole undertaking was cancelled.