'SG' (i) was the designation of Allied convoys (together with a numerical suffix) plying the route from Southend on the Thames estuary to Grimsby on the Humber estuary, and as such reciprocals of the 'GS' (i) series (March/April 1940).

The first of these 'Southend to Grimsby' coasting vessel convoys was SG.1 of 8/9 March 1940 with 24 ships, and the last SG.31 of 13/14 April 1940 with 14 ships.