Convoys SL 139/MKS 30 were two Allied convoys which ran during the Battle of the Atlantic in World War II. SL 139 was part of the OS/SL series, between Britain and the South Atlantic, and MKS 30 one of the KMS/MKS series between Britain and the Mediterranean. They were sailing together on the Gibraltar homeward route, having made a rendezvous off Gibraltar in November 1943. They were the subject of a major U-boat attack, as part of the German Navy’s (Kriegsmarine (KM)’s) renewed Autumn offensive.