Definition
An officer of the British royal household, historically ranking third among the great officers of that household, below the Lord Steward and the Lord Chamberlain. The office is, when it exists, always held by a peer of high rank. The Master of the Horse was originally responsible for the actual management and supervision of the sovereign's stables, horses, and related staff. That operational function has long since passed to a permanent career official — the Crown Equerry and Secretary to the Master of the Horse — leaving the Master of the Horse as a ceremonial and dignitary appointment. The traditional privilege associated with the office includes the right to make use of horses, footmen, and pages belonging to the royal stables.
Common Language
Modern common usage (Wiktionary): An equerry, especially the exalted official bearing this name at the British court; historically, a reference also extends to the ancient Roman Magister Equitum, the officer appointed by a Roman dictator to act as second-in-command.
Historical common usage (Webster's 1913): Not separately defined as a term of art; "master" in common usage referred broadly to one having authority or charge over others, and "horse" to the animal or a collective body of cavalry.
The gap here is one of specificity rather than contradiction. In ordinary usage, "master of the horse" might suggest anyone in charge of horses or cavalry. In the legal and constitutional sense, the term is a precise title of royal office — a defined position within the hierarchy of the British royal household, carrying formal privileges and a fixed rank in the order of precedence. The Roman usage (Magister Equitum) is a distinct office entirely and should not be conflated with the English royal appointment.
Why It Matters in Research
Researchers encountering this term in historical English legal sources — particularly materials touching on royal household law, court records, prerogative powers, or disputes involving royal servants and property — should be alert to the evolution of the office's practical authority. In older sources, the Master of the Horse appeared as an officer with genuine administrative power over the royal stables and considerable influence over the monarch's travel and ceremonial arrangements. Sources from the nineteenth century onward may reflect the bifurcation of the office, with operational authority transferred to the Crown Equerry, while the Master of the Horse retained ceremonial standing. Conflating the two officials in a historical research context could produce errors about who actually held decision-making authority in a given period.
This term also appears in the broader taxonomy of "great officers of the household" — a classification with legal significance in historical English law regarding precedence, privileges, and parliamentary standing. Researchers working through Rapalje & Lawrence should note that the printed entry as it appears in the source material appears to bleed into a separate, partially printed discussion of referees or masters in chancery — the phrase "hear summonses and applications in chambers, tax bills of costs, examine witnesses before trial" belongs to a distinct entry, likely for a different type of "master." This is a transcription or printing artifact and should not be read as part of the definition of Master of the Horse.
The Roman Magister Equitum, referenced in Wiktionary, is a separate institution entirely and surfaces in classical legal history and Roman law sources. Researchers working on Roman law, civil law history, or comparative constitutional history should not treat that usage as continuous with the English office.
Historical Dictionary Support
Black's Law Dictionary and Rapalje & Lawrence give nearly identical short-form definitions, locating the office as the third great officer of the royal household and identifying the privilege of use of royal stable resources. Both are accurate but skeletal — neither addresses the historical evolution of the role or the practical separation of functions that had already occurred by the time those editions were compiled.
Bouvier's Law Dictionary is the most informative of the three on the historical arc. Bouvier explicitly acknowledges that actual charge of the royal stables had passed to the Crown Equerry, correctly characterizing the Master of the Horse as a high-ranking honorary appointment by the time of writing. Bouvier also situates the office within the tripartite structure of principal household officers (Lord Steward, Lord Chamberlain, Master of the Horse), which is the constitutionally meaningful framing for understanding the position's place in the royal household hierarchy.
None of the dictionary sources addresses the parliamentary dimensions of the office — the fact that appointment as Master of the Horse has historically been a government appointment, meaning the position has carried political as well as ceremonial significance, changing hands with administrations. That gap is worth noting for researchers expecting the dictionaries to fully account for the office's constitutional role in English political history.
Jurisdictional Note
This is a term specific to the law and constitutional custom of England (and by extension the broader United Kingdom). It has no counterpart in American law. Researchers in comparative constitutional law or legal history may encounter analogous ceremonial household offices in other monarchies, but those are distinct institutions.