The office of Groom in Waiting (sometimes hyphenated as Groom-in-Waiting) was a post in the Royal Household of the United Kingdom, which in earlier times was usually held by more than one person at a time – in the late Middle Ages there might be dozens of persons with the rank, though the Esquires and Knights of the Body were more an important and select group.
Grooms-in-Waiting to other members of the Royal Family and Extra Grooms in Waiting were also sometimes appointed.
By the time of Queen Victoria, however, the majority of political offices no longer involving regular attendance on the sovereign, there were appointed, in addition to the Queen's Women of the Bedchamber, eight Grooms in Waiting who would discharge those political and social functions of the Grooms of the Bedchamber which could not be undertaken by the Queen's attendants of the female sex.
One of the holders of the office was designated the Parliamentary Groom in Waiting from about 1859, when it became customary to appoint a Member of Parliament who was a supporter of the government of the day.
The political office fell into disuse in 1892, since which time it has not been revived, although this did not affect the non-political, court position of Groom in Waiting.