Convoy SC 42 was the 42nd of the numbered series of World War II Slow Convoys of merchant ships from Sydney, Cape Breton Island to Liverpool. SC 42 was attacked over a three night period in September 1941, losing 16 ships sunk and 4 damaged. This was the worst Allied loss following the attack on convoy SC 7 the previous year. Two attacking U-boats were destroyed.

HMS Douglas was an Admiralty type flotilla leader of the British Royal Navy. Built by Cammell Laird, Douglas commissioned in 1918, just before the end of the First World War. During the Second World War, Douglas served with Force H out of Gibraltar and as a convoy escort. She was sold for scrap in March 1945.