The Eighth Army was a field army of the British Army during the Second World War. It was formed as the Western Army on 10 September 1941, in Egypt, before being renamed the Army of the Nile and then the Eighth Army on 26 September. It was created the better to control the growing Allied forces based in Egypt and to direct their efforts to lift the siege of Tobruk via Operation Crusader.

The Western Desert campaign took place in the deserts of Egypt and Libya and was the main theatre in the North African campaign of the Second World War. Military operations began in June 1940 with the Italian declaration of war and the Italian invasion of Egypt from Libya in September. Operation Compass, a five-day raid by the British in December 1940, was so successful that it led to the destruction of the Italian 10th Army over the following two months. Benito Mussolini sought help from Adolf Hitler, who sent a small German force to Tripoli under Directive 22. The Afrika Korps was formally under Italian command, as Italy was the main Axis power in the Mediterranean and North Africa.