The XXI Corps was an Army Corps of the British Army during World War I. The Corps was formed in Palestine in August 1917 under the command of Lieutenant General Edward Bulfin. It formed part of the Egyptian Expeditionary Force (EEF) and served in the Sinai and Palestine Campaign. At the Battle of Sharon it fought what has been described as 'one of the most overwhelmingly successful operations of the war' and 'a precursor to the modern Blitzkrieg.' It then carried out remarkable march up the coast of modern-day Lebanon as the war came to an end.

General Sir Edward Stanislaus Bulfin was a British general during World War I, where he established a reputation as an excellent commander at the brigade, divisional and corps levels. He was most noted for his actions during the First Battle of Ypres, when he organized impromptu forces to slow down the German assault.