The British Army is the land warfare branch of the British Armed Forces of the United Kingdom. It came into being with the unification of the Kingdoms of England and Scotland into the Kingdom of Great Britain in 1707. The new British Army incorporated Regiments that had already existed in England and Scotland and was administered by the War Office from London. It has been managed by the Ministry of Defence since 1964. The professional head of the British Army is the Chief of the General Staff, currently General Sir Peter Wall.

The full-time element of the British Army is referred to as the Regular Army and has been since the creation of the reservist Territorial Force in 1908. All members of the Army swear (or affirm) allegiance to the monarch as commander-in-chief. However the Bill of Rights of 1689 requires Parliamentary consent for the Crown to maintain a standing army in peacetime. Parliament therefore annually approves the continued existence of the Army. In contrast to the Royal Navy, Royal Marines and Royal Air Force, the British Army does not include Royal in its title. Many of the Army's constituent Regiments and Corps have been granted the "Royal" prefix and have members of the Royal Family occupying senior positions within some regiments.