British (United Kingdom) officer of state who is custodian of the great seal and a cabinet minister. The lord chancellor traditionally served as head of the judiciary and speaker of the House of Lords (Lords, House of). In 2006, however, the post's role was redefined following the implementation of several constitutional reforms. Most of the lord chancellor's judicial functions were transferred to the lord chief justice, and the Lords speaker became an elected office. The changes allowed the lord chancellor to concentrate on constitutional affairs.

The office dates back to Edward the Confessor (1042–66), who followed the model of the Carolingian (Carolingian dynasty) court when he appointed a chancellor. Until the 14th century the chancellor was invariably a priest and served as royal chaplain, the king's secretary in secular matters, and keeper of the royal seal. All of the secretarial work of the royal household was handled by the chancellor and his staff of chaplains; the accounts were kept under the justiciar and treasurer, writs were drawn up and sealed, and the royal correspondence was carried out. This combination of duties, characteristic of the primitive administrative systems of the early Middle Ages, remained with the chancellorship into the early 21st century, although most of the office's power, exemplified in the administrations of such great chancellors as Thomas Becket (Becket, Saint Thomas) (d. 1170) and Thomas Cardinal Wolsey (Wolsey, Thomas, Cardinal) (d. 1530), ceased to exist centuries ago.

Much of the reason that the English chancellor did not develop into the head of government, as did his counterpart in the Holy Roman Empire, lies in the growth of his judicial duties. All petitions addressed to the king passed through the chancellor's hands, and by the reign of Henry II (1154–89) the chancellor's time was already largely taken up with judicial work. The office acquired a more definitely judicial character in the reign of Edward III (1327–77), when the chancellor's court ceased to follow the king. The chancellor's court was the direct precursor of the Court of Chancery (Chancery, Court of), which was fused into the High Court of Justice in the Judicature Act of 1873. The Chancery Division of the latter is primarily responsible for equitable jurisdiction.

The position of the chancellor as speaker, or prolocutor, of the House of Lords dated from the time of the English Norman kings, when the ministers of the Curia Regis (“King's Court”) sat ex officio in the commune concilium (“great council”) and Parliament. When the other officials ceased to attend Parliament, the chancellor continued to do so. He attended by virtue of his office, but since the early 18th century he has invariably been a peer. As speaker of the House of Lords, he differed considerably in his powers and duties from the speaker of the House of Commons (Commons, House of). Although he put the question (i.e., call for a vote), he had no power to rule upon points of order. Unlike the speaker of the House of Commons, he often took part in debates.

When the chancellor was present in the House of Lords, he presided from the Woolsack, a seat introduced by Edward III and originally stuffed with English wool as a symbol of England's prosperity. (As a symbol of unity, the Woolsack was later stuffed with wool from countries of the British Commonwealth.) The responsibilities of the lord chancellor necessitated his frequent absence from the House of Lords, and on these occasions the house was chaired by a deputy speaker. Because of the weight of administrative business since 1939, modern chancellors had less time for judicial duties.

The chancellor also had certain powers of ecclesiastical patronage. For many years it was thought that Roman Catholics were barred from holding the office. However, Parliament clarified the law in 1974, approving a bill that stated that Roman Catholics could be appointed lord chancellor.

In the early 21st century there were calls to abolish the lord chancellorship. Much criticism centred on the fact that the office held important responsibilities in different branches of government. In 2003 a new post was created, secretary of state for constitutional affairs, that was scheduled to replace the lord chancellorship. However, there was support for retaining the historic post, and after much debate Parliament approved the Constitutional Reform Act 2005, which preserved the office but redefined its role. Since 2007 the lord chancellor has also held the title of secretary of state for justice.