The British Army is the land warfare branch of Her Majesty's Armed Forces in 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 1963.

As of February 2011 the British Army employs 106,550 Regulars, 3,880 Gurkhas and 33,130 Territorials for a total combined component strength of 143,550 Soldiers. In addition there are 134,190 Regular Reserves of the British Army. The British Army is the largest army in the European Union. The full-time element of the British Army has also been referred to as the Regular Army since the creation of the reservist Territorial Force in 1908. The British Army is deployed in many of the world's war zones as part of both Expeditionary Forces and in United Nations Peacekeeping forces. The British Army is currently deployed in Kosovo, Cyprus, Germany, Afghanistan and many other places.

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.

The professional head of the British Army is the Chief of the General Staff, currently General Sir Peter Wall KCB CBE ADC Gen.