'CK' (iii) was the designation of Allied convoys (together with a numerical suffix) plying the route from Charleston, on the eastern coast of the USA, to the UK (January/November 1944).

The first of the series was CK.1 which departed Charleston, South Carolina on 20 January 1944 with eight commissioned ships in the form of the 1,030-ton fleet tug Keywaydin, the minesweepers Owl, Threat and Tide, and the submarine chasers PC-484, PC-1176 and PC-1261. The last was CK.4 which departed Charleston on 6 November 1944 with five commissioned ships in the form of the 5,450-ton oiler Mattole escorted by the destroyer escorts Fogg, George W. Ingram, Ira Jeffery and Lee Fox.