Rationing was introduced temporarily by the British government several times during the 20th century, during and immediately after a war.At the start of the Second World War in 1939, the United Kingdom was importing 20 million long tons of food per year, including about 70% of its cheese and sugar, almost 80% of fruit and about 70% of cereals and fats. The UK also imported more than half of its meat and relied on imported feed to support its domestic meat production. The civilian population of the country was about 50 million. It was one of the principal strategies of the Germans in the Battle of the Atlantic to attack shipping bound for Britain, restricting British industry and potentially starving the nation into submission.

To deal with sometimes extreme shortages, the Ministry of Food instituted a system of rationing. To buy most rationed items, each person had to register at chosen shops and was provided with a ration book containing coupons. The shopkeeper was provided with enough food for registered customers. Purchasers had to present ration books when shopping so that the coupon or coupons could be cancelled as these pertained to rationed items. Rationed items had to be purchased and paid for as usual; rationing restricted what items and what amount could be purchased. Items that were not rationed could be scarce. Prices of some unrationed items were controlled; prices for items not controlled could be unaffordably high for many people.

During the Second World War rationing—not restricted to food—was part of a strategy including controlled prices and government-enforced standards, with the goals of managing scarcity and prioritising the armed forces and essential services, and trying to make available to everyone an adequate supply of goods of acceptable quality.