The Royal Regiment of Horse Guards, also known as the Blues, or abbreviated as RHG, was one of the cavalry regiments of the British Army and part of the Household Cavalry. In 1969, it was amalgamated with the 1st The Royal Dragoons to form the Blues and Royals.

Raised in August 1650 by Sir Arthur Haselrig on the orders of Oliver Cromwell, following the 1660 Stuart Restoration, it became the Earl of Oxford's Regiment in 1660. Based on the colour of their uniform, the regiment was nicknamed "the Oxford Blues", or simply the "Blues." In 1750, it became the Royal Horse Guards Blue and eventually, in 1877, the Royal Horse Guards (The Blues).

The Royal Regiment of Horse Guards has its origins in the Regiment of Cuirassiers, raised by Sir Arthur Haselrig on the orders of Oliver Cromwell at Newcastle upon Tyne and County Durham in August 1650. It was initially disbanded following the 1660 Stuart Restoration, before being re-constituted in the wake of the Venner Riots and creation of the English Army on 26 January 1661. The colonelcy of the new regiment was given to Aubrey de Vere, 20th Earl of Oxford, and the regiment first paraded at Tothill Fields in London on 6 February 1661.

Early duties focused on internal policing and domestic security, with three troops based primarily in Canterbury, Southwark, and Bagshot. When James II of England succeeded in February 1685 it was recalled to do policing duties in London. John Churchill, later Earl of Marlborough deserted the royal household to greet William, Prince of Orange in 1688. The following year The Blues were part of the allied army that defeated the French at Walcourt, near Charleroi, when they charged the best French infantry, leaving 2,000 dead.

During the early eighteenth century the Blues were widely dispersed throughout the north country. Following the outbreak of the War of the Austrian Succession in 1740, the Royals became part Honywood's brigade, arriving in Flanders in August 1742. An account of the campaign was provided by Dr John Buchanan, the regimental surgeon. The unit took part in the 1743 Battle of Dettingen, after which the Household Cavalry Brigade was formed for the first time, comprising the Life Guards, Horse Grenadiers, and Blues.

During the Seven Years' War, the Blues fought alongside Prince Ferdinand. The largest cavalry regiment, The Blues colonelcy was assumed by John Manners, Marquess of Granby. This great soldier understood the importance of morale. In the mould of John Ligonier, 1st Earl Ligonier, a predecessor, he established a brave and efficient force. His successor, Henry Seymour Conway was one of the greatest colonels the regiment ever had over a 25-year period. Granby however, retained a passionate interest in the welfare of The Blues; his generosity and hospitality expressed later in a legion of public houses. Granby was in charge of the second division at Battle of Minden Heath in August 1759. The Blues posted sentries called Vedettes, who were so close when the French attacked that the regiment was thrown back. The Blues were eager to charge in after the infantry surge to Minden walls, but owing to Lord George Sackville's orders the reinforcements were delayed. Sackville was court-martialled and found guilty of disobeying orders.

The allies had saved Hanover, and driven Marshal Louis Georges Érasme de Contades back towards the Rhine. By December 1759 The Blues were exhausted looking forward to a winter break at Osnabrück. Lieutenant-Colonel Johnston went to recruit in England; and found the Dragoon Guards who wanted to join for the superior conditions in The Blues. Granby was depressed by his son's death and that of his wife too, and the loss of his stud, so he decided to set up a Widows' Fund, and to provide better regimental medical care. His cousin, Russell Manners was raised to battalion command; and King George II's interest in The Blues was inherited by George III. Granby commanded The Blues and The Royals on their march south from Paderborn. At Warburg on 31 July 1760, The Blues lined up in the centre. The British force of 8,000 stole a march on the French positions, and charging headlong into the enemy dispersed a force of 24,000. The famous 'Charge' on trumpet and bugle sent Granby's men into history:

For we Rout'd all before us – Down precipices, over hollow ways we went like a torrent as the French general term'd it, which struck such a panick so that they [led] without firing a shot. The Marquis of Granby pursued the enemy above 10 miles.