Horse Guards is a historic building in the City of Westminster, London, between Whitehall and Horse Guards Parade. It was built in the mid-18th century, replacing an earlier building, as a barracks and stables for the Household Cavalry. The current and previous buildings were, between the early 18th century and 1858, the main military headquarters for the British Empire. Horse Guards originally formed the entrance to the Palace of Whitehall and later St James's Palace; for that reason it is still ceremonially defended by the King's Life Guard.

The Household Cavalry (HCAV) is a corps of the Household Division, made up of the two most senior regiments of the British Army, The Life Guards and The Blues and Royals. These regiments are divided between the Household Cavalry Regiment stationed at Wing Barracks in Wiltshire, with an armored reconnaissance role, and the ceremonial mounted unit, the Household Cavalry Mounted Regiment, garrisoned at Hyde Park Barracks in London. Both the HCMR and HCR are made up of elements of the Life Guards and the Blues and Royals. The Household Cavalry is part of the Household Division and is the King's official bodyguard. Although the Household Cavalry Regiment is armoured, it is not part of the Royal Armoured Corps, being assigned to the Household Division.