The 3rd Dragoon Guards was a cavalry regiment in the British Army, first raised in 1685 as the Earl of Plymouth's Regiment of Horse. It was renamed as the 3rd Regiment of Dragoon Guards in 1751 and the 3rd Dragoon Guards in 1765. It saw service for two centuries, including the First World War, before being amalgamated into the 3rd/6th Dragoon Guards in 1922.

There are 13 cavalry Regiments of the British Army each with its own unique cap badge, regimental traditions, and history. Of the currently nine regular cavalry regiments, two serve as armoured regiments, three as armoured cavalry regiments, three as light cavalry, and one as a mounted ceremonial regiment. There are also four yeomanry regiments of the Army Reserve, of these, three serve as light cavalry and one as an armoured regiment. Each yeomanry light cavalry unit has been paired with a regular unit of the same role, the armoured yeomanry unit is paired with the two regular armoured units. All except the Household Cavalry are part of the British Army's Royal Armoured Corps.