The leader of the House of Lords is a member of the Cabinet of the United Kingdom who is responsible for arranging government business in the House of Lords. The post is also the leader of the majority party in the House of Lords who acts as the government party chairperson in the house. The role is always held in combination with a formal Cabinet position, usually one of the sinecure offices of Lord President of the Council, Lord Keeper of the Privy Seal or Chancellor of the Duchy of Lancaster. Unless the Leader is also a departmental minister, being Leader constitutes the bulk of their government responsibilities, but it has never been an independent salaried office. The Office of the Leader of the House of Lords is a ministerial department.

Though the leader of the House is a member of the cabinet and remains a partisan figure, the leader also has responsibilities to the House as a whole. In contrast to the House of Commons, where proceedings are controlled by the speaker, proceedings in the Lords are controlled by peers themselves, under the rules set out in the Standing Orders. The leader of the House has the responsibility of reminding the House of these rules and facilitating the Lords' self-regulation, though any member may draw attention to breaches of order or failure to observe customs. The Leader is often called upon to advise on procedures and points of order and is required to determine the order of speakers on Supplementary Questions, subject to the wishes of the House. However, like the Lord Speaker, the Leader of the House has no power to rule on points of order or to intervene during an inappropriate speech.

Until the election of the first Lord Speaker on 4 July 2006, the Leader of the House had responsibility for making preliminary decisions on requests for Private Notice Questions and for waiving the sub judice rule in certain cases. Those functions were transferred to the Lord Speaker.