'UG' was the designation of US military convoys (together with a numerical and sometimes a literal suffix) plying the route from the USA to North Africa for the delivery of troops allocated to 'Torch' and then subsequent operations in North Africa and the western part of the Mediterranean, and as such reciprocals of the 'GU' series (October 1942/April 1945).

Also tasked with the subsequent delivery of food, ammunition and matériel to the US forces in North Africa and southern Europe, these 'USA to Gibraltar' convoys assembled in Hampton Roads near the mouth of Chesapeake Bay and terminated in various North African locations as Axis forces retreated from 1942 to 1945. Allied matériel had been carried from North America to the UK in 'HX' convoys since 1939 and in slower 'SC' convoys since 1940, both types being escorted by ships of the Royal Navy and Royal Canadian Navy, and from September 1941 to April 1943 by a few escorts of the US Navy.

The 'UG' convoy type was established as a more direct supply route for the support of the invasion of North Africa, and had three subdivisions as the 'UGF' fast convoys, 'UGL' landing craft convoys and 'UGS' slow convoys.

The first convoy, designated UGF.1, was the invasion convoy, and departed Hampton Roads on 24 October 1942 with 36 laden transport vessels and an eventual total of 62 escorts, and this arrived on 8 November 1942.

The letter F designated a convoy of faster ships. Thereafter, fast and slow eastbound and westbound convoys on this southern route were given four separate numbering sequences beginning with 2. On average, one eastbound fast convoy departed Hampton Roads each month along the southern trans-Atlantic route beginning with convoy UGF.2 on 2 November 1942. The UGF.2 and UGF.3 convoys terminated in Casablanca in 1942. The UGF.4 to UGF.10 convoys terminated in Oran in 1943. The UGF.8 and UGF.9 convoys each sailed in two sections with the second section identified as UGF.8A and UGF.9A respectively. Fast convoys were temporarily suspended during preparation for 'Neptune' (iii) and 'Overlord' after the UGF.10 convoy had reached Oran on 2 September 1943. Sailings resumed on 17 May 1944, and the UGF.11 to UGF.21 convoys passed through the Strait of Gibraltar to terminate in Naples during 1944 and 1945, though the separate UGF.15B and UGF.17B convoys terminated in Marseille. The last eastbound fast convoy was UGF.22, which terminated in Oran on 8 April 1945.

A total of 382 ships sailed in 26 fast convoys, and none was lost.

About two eastbound slow convoys departed Hampton Roads each month along the southern trans-Atlantic route, beginning with the UGS.2 convoy on 13 November 1942. The departure frequency increased to three convoys per month in the summer of 1943 and increased again to six convoys per month in 1945. The last slow eastbound convoy was UGS.95, which departed Hampton Roads on 28 May 1945 on the following day.

About 5,800 ships sailed in 100 slow convoys, whose additional sections were identified as UGS.5A, UGS.6A, UGS.7A, UGS.8A, UGS.33A, and UGS.55B.

The UGS.6 convoy of March 1943 was attacked by the 'Unverzagt', 'Wohlgemut' and 'Tümmler' wolfpacks and lost the 8,062-ton French freighter Wyoming to Kapitänleutnant Walter Freiherr von Steinaecker’s U-524 on 15 March, 7,191-ton US freighter Benjamin Harrison to Kapitänleutnant Carl Emmermann’s U-172 on 16 March, and 7,200-ton US freighter Molly Pitcher to Kapitänleutnant Kurt Neubert’s U-167 and Kapitänleutnant Klaus Heinrich Bargsten’s U-521 on 17 March. These were the only ships lost during these convoys' Atlantic crossings, although another 16 were lost in the Mediterranean.

Some 335 ships returned to the USA along the southern transatlantic route in 24 fast convoys beginning with the GUF.2 convoy which departed Casablanca on 29 November 1942. The last westbound fast convoy was GUF.22, which departed Oran on 16 April 1945. Additional sections were identified as GUF.2A, GUF.15B and GUF.7B. No ships were lost from these fast convoys. Some 5,200 ships returned to the USA along the southern transatlantic route in 98 slow convoys beginning with the departure of the GUS.2 convoy from Oran on 21 December 1942.

The last westbound slow convoy was GUS.92 that departed Oran on 27 May 1945. Additional sections were identified as the GUS.5A, GUS.5B, GUS.6A, GUS.7A, GUS.8A, GUS.10X and GUS.55B convoys. There were no losses from these convoys during the Atlantic portion of their voyages, but five ships were lost in the Mediterranean.

Fast troopship convoys were accompanied by battleships or cruisers as protection against surface raiders. The US Navy provided all escort between Hampton Roads and Gibraltar, although some of the destroyer escorts providing anti-submarine screens for these convoys had US Coast Guard crews. Most of the convoys were given air coverage from escort carriers and patrol bombers flying from the Azores islands group. The Royal Navy initially provided escorts within the Mediterranean, although the US Navy escorted these convoys as far as Oran as the North African front moved to the east.