The Lord High Chancellor of Great Britain, or Lord Chancellor is a senior and important functionary in the government of the United Kingdom. He is the second highest ranking of the Great Officers of State and is appointed by the Sovereign on the advice of the Prime Minister. Prior to the Union there was a separate Chancellor of England and Lord Chancellor of Scotland.

One of the Lord Chancellor's responsibilities is to act as the custodian of the Great Seal. He is a member of the Cabinet and, by law, is responsible for the efficient functioning and independence of the courts. Formerly he was also the presiding officer of the House of Lords, and the head of the judiciary in England and Wales, but the Constitutional Reform Act 2005 transferred these roles to the Lord Speaker and the Lord Chief Justice respectively. The present Lord Chancellor, The Rt.Hon. Jack Straw, is also Secretary of State for Justice, and the first Lord Chancellor since the seventeenth century not to be a peer. His predecessor, Lord Falconer of Thoroton served as Secretary of State for Constitutional Affairs before that post was superseded by the post of Secretary of State for Justice in 2007.

A Lord Keeper of the Great Seal may be appointed instead of a Lord Chancellor. The two offices entail exactly the same duties; the only distinction is in the mode of appointment. Furthermore, the office of Lord Chancellor may be exercised by a committee of individuals known as "Lords Commissioners of the Great Seal". Since the 19th century, however, Lord Chancellors have been exclusively appointed, the other offices having fallen into disuse.