Lieutenant general, formerly more commonly lieutenant-general, is a senior rank in the British Army and the Royal Marines. It is the equivalent of a multinational three-star rank; some British lieutenant generals sometimes wear three-star insignia, in addition to their standard insignia, when on multinational operations.

I Corps was an army corps in existence as an active formation in the British Army for most of the 80 years from its creation in the First World War until the end of the Cold War, longer than any other corps. It had a short-lived precursor during the Waterloo Campaign. It served as the operational component of the British Army of the Rhine during the Cold War, and was tasked with defending West Germany.