Convoy JW 51B was an Arctic convoy sent from United Kingdom by the Western Allies to aid the Soviet Union during World War II. It sailed in late December 1942, reaching the Soviet northern ports in early January 1943. JW 51B came under attack by German surface units, engaged in Operation Regenbogen, on 31 December. In the clash that ensued, one defending minesweeper and one attacking destroyer were sunk with all hands and a defending destroyer was sunk; no ships were lost from the convoy. This engagement became known as the Battle of the Barents Sea.