The Parliamentary Archives of the United Kingdom preserves and makes available to the public the records of the House of Lords and House of Commons back to 1497, as well as some 200 other collections of parliamentary interest. The present title was officially adopted in November 2006, as a change from the previous title, the House of Lords Record Office.

The over three million records are stored at The National Archives in Kew. Some of the most important constitutional records of the United Kingdom are in the collection, including the Petition of Right (1628), the Death Warrant of Charles I (1649), the Habeas Corpus Act 1679, the draft and final Bill of Rights (1689), the Slave Trade Act (1807 and 1833), the Great Reform Act (1832), and successive Representation of the People Acts. The archive was previously housed in the Victoria Tower at the Palace of Westminster, but was moved to its current location in 2025.

The archives also oversees records management for Parliament, has an active outreach programme and frequently appears on radio and TV programmes.

The archive of the House of Lords originated in March 1497, when the then Clerk, Master Richard Hatton, having prepared the Parliament Roll for that session for transfer to Chancery, retained in the House of Lords the complete series of sixteen enacted Bills, or Original Acts, from which he had made the enrolment. Since then, this series has been preserved continuously among the records of the House of Lords.

By 1509, the Clerk of the Parliaments and his assistants (today known collectively as the Parliament Office) had hived off from Chancery, and in the course of the 16th century this newly independent Lords office gradually expanded and formalised its record keeping. In addition to the class of Original Acts already mentioned, the clerks preserved Journals of the House of Lords, now surviving from 1510, Petitions from 1531 and Bills from 1558. It seems, however, that the office was somewhat haphazard in its methods; Cardinal Wolsey, for instance, when Lord Chancellor, is said to have removed all the Acts and Journals relating to one session. A more business-like administration began with the advent of two Clerks in the 17th century, Robert Bowyer (1609–1621) and Henry Elsynge (1621–1635). Under these diligent and scholarly men the Lords archive took its modern form. Petitions and many other forms of Papers coming to the Lords were carefully filed; extensive series of rough Minutes and of Committee Proceedings were preserved; and, not least in importance, the records were assigned a permanent home at the south west corner of the Palace of Westminster, in a moated building (still surviving, and open to the public), the 14th-century Jewel Tower. Here the principal records of the Lords remained from 1621 to 1864, being available throughout this period for inspection by the public. The contents of some were given still wider currency in the 18th century as certain Bills and Papers began to be printed, and when, in 1767, the Lords ordered the printing of their Journals.

Meanwhile, a second parliamentary archive, the records of the House of Commons, had been forming in another part of the Palace of Westminster. Initially, in the Middle Ages, it could be said that no formal records at all were made of the domestic proceedings of the House of Commons. From 1547, however, a Commons Journal survives, and, parallel with the formation in the Lords of the main Parliamentary records under Bowyer and Elsynge, separate series of domestic records of the Commons began to accumulate, of Petitions and Papers (from the reign of Elizabeth I), of Return Books of Elections (from 1625) and of Minute Books of Committees (from 1623).

By the early 19th century the House of Commons archive was extensive, but on the night of 16 October 1834 almost the entire stock—with the vital exception of the Commons Journals—was consumed in the "tally stick fire", which destroyed a great part of the fabric of the Palace of Westminster. The records had been stored in the House of Commons Library and various attics throughout the Commons, all of which went up in smoke.

The House of Lords archive, however, survived. This was in part due to the isolated position of the Jewel Tower, where the main series of records had been preserved, but also in part owing to the efforts of a Lords clerk, Henry Stone Smith, who threw out of the blazing windows of the main building onto Old Palace Yard many hundreds of bundles of other Lords papers that had not been transferred to the Jewel Tower. These bundles for several decades after the fire led a confused existence, being virtually forgotten by those outside the Parliament Office, until, in 1870, the newly formed Royal Commission on Historical Manuscripts began to issue regular reports. In them, the commission drew attention to the extent and variety of manuscripts preserved in the House of Lords. The first Report of the Commission brought to light a packet of letters which had been abandoned by Charles I at the Battle of Naseby, as well as the "annexed" Book of Common Prayer of 1662, the Declaration of Breda, and other public muniments which had "just been untombed from this mausoleum of historic remains" (as Thomas Duffus Hardy and his fellow Commissioners remarked). The succeeding Reports of the Commissioners were continued from 1900 onwards by calendars published by the House of Lords itself.