'QS' was the designation of Allied convoys (together with a numerical and in one case a literal suffix) plying the route from Quebec to Sydney, Nova Scotia, as as such reciprocals of the 'SQ' series (May 1942/December 1944).

There were 110 such convoys, of which the first was QS.1 of 17/19 May 1942 with the 5,363-ton British Corrales, 6,431-ton British Dorelian, 6,966-ton British Indochinois, 5,859-ton Belgian Jean Jadot, 5,106-ton British King Frederick, 7,071-ton British Manchester Port, 3,022-ton Norwegian Mosdale and 5,021-ton British Torr Head, and the last QS.109 of 14/16 December 1944 with the 4,970-ton British Empire Shearwater and 7,335-ton British Lord Strathcona.