'CJ' was the designation of Allied convoys (together with a numerical and sometimes a literal suffix) plying the route from Calcutta, India, to Colombo, Ceylon, and as such reciprocals of the 'JC' series (April 1943/January 1945).

The series began with CJ.1A of 2/5 April 1943 with the 5,348-ton British Tolten and 8,814-ton Norwegian Troja, and ended with CJ.44B of 24 December 1944/1 January 1945) with the 2,888-ton Norwegian Belray.