The Royal Commission on Historical Manuscripts (widely known as the Historical Manuscripts Commission, and abbreviated as the HMC to distinguish it from the Royal Commission on the Historical Monuments of England), was a United Kingdom Royal Commission established in 1869 to survey and report on privately owned and privately held archival records of general historical interest. Its brief was "to make inquiry as to the places in which such Manuscripts and Papers were deposited", and to report on their contents. It remained in existence until 2003, when it merged with the Public Record Office to form The National Archives. Although it technically survives as a legal entity, its work is now entirely subsumed into that of The National Archives.

Following the passing of the Public Record Office Act 1838, which made statutory provision for the care of government archives, pressure began to grow for the state to pay attention to privately owned records. Largely on the initiative of Lord Romilly, the Master of the Rolls, the first Royal Commission on Historical Manuscripts was appointed by Royal Warrant dated 2 April 1869. The first Commissioners were Romilly himself (as chairman); the Marquess of Salisbury; the Earl of Airlie; Earl Stanhope; Lord Edmοnd Petty-Fitzmaurice; Sir William Stirling-Maxwell; Charles Russell, President of Maynooth College; George Webbe Dasent; and T. D. Hardy, Deputy Keeper of the Records. They were shortly afterwards joined by George Butler, Bishop of Limerick; and Lord Talbot de Malahide. A new Royal Warrant of 1876 confirmed the appointment of what had effectively become a standing commission; and the Commission's work was extended by further warrants dated 18 December 1897 and 27 March 1919.

Four inspectors (including H. T. Riley) were appointed in 1869 to survey records under the Commissioners' direction. Later inspectors included Henry Maxwell Lyte, John Knox Laughton, Joseph Stevenson, Reginald Lane Poole, W. D. Macray, J. K. Laughton, Horatio Brown, W. J. Hardy and John Gwenogvryn Evans.

Throughout the 19th and early 20th century the Commission remained closely associated with the Public Record Office: indeed, in 1912 it was stated that "for all practical purposes the Commission itself may be regarded as a branch of the Record Office". However, in the wake of the Public Records Act 1958 (which transferred responsibility for public records to the Lord Chancellor, while the Commission remained under the authority of the Master of the Rolls) the two bodies diverged to achieve a greater degree of independence from one another. A new Royal Warrant, dated 5 December 1959, gave the Commission revised and greatly extended terms of reference. Over the next few decades the Secretaries to the Commission included Roger Ellis, 1957–72, Godfrey Davis, 1972–82, Brian Smith, 1982–92 and Christopher Kitching, 1992–2004.

This period of independence ended in April 2003, when another Royal Warrant effectively merged the Commission with the PRO to form the new National Archives. The Chief Executive and Keeper of Public Records is now the sole Historical Manuscripts Commissioner, while the role of Secretary of the Commission is combined with that of Head of Archives Sector Development. Since the creation of The National Archives the role of Secretary of the Commission has been filled by Nicholas Kingsley, 2005–15 and Isobel Hunter, 2015–date.

Until 1945, the principal medium through which the Commission disseminated its findings was publication: thereafter, it developed other channels of communication (notably the National Register of Archives: see below), but publication always remained important.

Throughout its existence, the Commission published periodical reports to the Crown in the form of command papers. The reports themselves were relatively brief and conventional, but in the early years they were accompanied by lengthy appendixes comprising detailed descriptions of the archival collections that had been inspected, in a combination of lists, calendars and transcripts of selected documents. The first such report was published, as a folio volume, in 1870: the appendix included reports on the manuscript collections of 44 corporate bodies and 36 private owners in England, Wales, Scotland and Ireland, and one located overseas (English manuscripts at Heidelberg University). Eight further reports, with increasingly detailed appendixes, were issued over the following years, the ninth and last in folio format appearing in 1883–4. Although the contents of many of the appendixes have been superseded by more comprehensive publications and finding aids, this is not invariably the case, and a number of the early reports continue to be used by researchers.

From its 10th report (1885) onwards the Commission switched to an octavo format, although it continued to include significant material in appendixes down to the 15th report (1899). In the same period, however, it began to publish its more detailed reports on collections as separate octavo volumes (or, in many cases, multi-volume series), with the material predominantly presented in calendar form. Over the next century it published some 200 such volumes before the series was discontinued: the final volume (the fifth in a series on the papers of the Finch family) appeared in 2004.