The Public Record Office[a] (abbreviated as PRO, pronounced as three letters and referred to as the PRO), Chancery Lane in the City of London, was the guardian of the national archives of the United Kingdom from 1838 until 2003, when it was merged with the Historical Manuscripts Commission to form The National Archives, based in Kew.

[5] Some of the records were court or departmental archives (established for several centuries) which were well-run and had good or adequate catalogues; others were little more than store-rooms.

These charges were abolished for serious historical and literary researchers after a petition was signed in 1851 by 83 people including Charles Dickens and the historians Lord Macaulay and Thomas Carlyle.

[7] The growing size of the archives held by the PRO and by government departments led to the Public Records Act 1958, which sought to avoid the indiscriminate retention of huge numbers of documents by establishing standard selection procedures for the identification of those documents of sufficient historical importance to be kept by the PRO.

Even so, growing interest in the records produced a need for the Office to expand, and in 1977 a second building was opened at Kew in south-west London.

The National Archives of Scotland and the Public Record Office of Northern Ireland were and remain separate institutions.