The North Sea Mine Barrage, also known as the Northern Barrage, was a large minefield laid easterly from the Orkney Islands to Norway by the United States Navy during World War I. The objective was to inhibit the movement of U-boats from bases in Germany to the Atlantic shipping lanes bringing supplies to the British Isles. Rear Admiral Lewis Clinton-Baker, commanding the Royal Navy minelaying force at the time, described the barrage as the "biggest mine planting stunt in the world's history." Larger fields with greater numbers of mines were laid during World War II.

A naval mine is a self-contained explosive device placed in water to damage or destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, any vessel or a particular vessel type, akin to anti-infantry or anti-vehicle mines. Naval mines can be used offensively, to hamper enemy shipping movements or lock vessels into a harbour; or defensively, to protect friendly vessels and create "safe" zones. Mines allow the minelaying force commander to concentrate warships or defensive assets in mine-free areas giving the adversary three choices: undertake an expensive and time-consuming minesweeping effort, accept the casualties of challenging the minefield, or use the unmined waters where the greatest concentration of enemy firepower will be encountered.