The Official Opposition Shadow Cabinet, or His Majesty’s Most Loyal Opposition Shadow Cabinet, but usually simply the Shadow Cabinet, is the committee of senior members of the Official Opposition who scrutinise the work of the Cabinet of the United Kingdom. Each Shadow Cabinet member is typically given a position which corresponds to that of a government minister in Cabinet. Shadow Cabinet members, known as Shadow Ministers, are usually appointed by the Leader of the Opposition. The roles of Shadow Ministers are to develop alternative policies, hold the government to account for its actions and responses, and act as spokespeople for the opposition party in their own specific policy areas. By convention, Shadow Ministers are drawn either from serving members of the House of Commons or the House of Lords, with most chosen from the former. Since May 2010, Labour has been the Official Opposition, and its leadership therefore forms the current Shadow Cabinet.

The Cabinet of the United Kingdom is the senior decision-making body of His Majesty's Government. A committee of the Privy Council, it is chaired by the Prime Minister and its members include Secretaries of State and other senior ministers. Members of the Cabinet are appointed by the Prime Minister and are by convention chosen from members of the two houses of the Parliament of the United Kingdom, the House of Commons and the House of Lords.