'NK' was the designation of Allied convoys (together with a numerical suffix) plying the route from New York to Key West, Florida, and as such reciprocals of the 'KN' series (August 1942/May 1945).

The first of 164 such 'New York to Key West' convoys was NK.500 of 28 August/3 September 1942 with two Norwegian, one British and one Swedish vessel, and the last was NK.686 of 10/12 May 1945 with 30 US, one Belgian and one British vessels.