'JS' was the designation of Allied convoys (together with a numerical and, in one case, a literal suffix) plying the route from Colombo, Ceylon, to Singapore, and as such reciprocals of the 'SJ' series (February 1942).

The first of these 'Colombo to Singapore' convoys was JS.1 of 3/14 February 1942 from Colombo to Batavia, Netherlands East Indies with the 7,905-ton British Adrastus carrying motor transport, 4,986-ton British Alice Moller, 4,856-ton British Filleigh carrying medical stores, 3,616-ton Norwegian Hai Lee carrying medical stores, 5,202-ton Norwegian Hermion, 7,628-ton British Lulworth Hill carrying stores, 9,070-ton British Modasa carrying ammunition, Prominent, and 8,131-ton British Yoma carrying troops. The last convoy of this short series, designed to strengthen the ABDA Command forces seeking to hold the Netherlands East Indies, was the JS.4 convoy of 24/26 February 1942 from Colombo for dispersal with the 24,289-ton US commissioned transport Mount Vernon.