'NSM' was the designation of a British convoy (together with a numerical suffix) plying the route from Scapa Flow in the Orkney islands group to Narvik in northern Norway (April 1940).

The sole such convoy was NSM.1 of 17/19 April with seven British ships in the form of the 1,428-ton Balmaha, 4,637-ton Blackheath, 4,836-ton Charlbury, 5,578-ton Inverarder, 964-ton Lochee, 3,379-ton Lombardy and 4,992-ton MacGregor Laird.