The shadow cabinet or shadow ministry is a feature of the Westminster system of government. It consists of a senior group of opposition spokespeople who, under the leadership of the Leader of the Opposition, form an alternative cabinet to that of the government, and whose members shadow or mirror the positions of each individual member of the Cabinet. Their areas of responsibility, in parallel with the ruling party's ministries, may be referred to as a shadow portfolio. Members of a shadow cabinet have no executive power. It is the shadow cabinet's responsibility to scrutinise the policies and actions of the government, as well as to offer alternative policies. The shadow cabinet makes up the majority of the Official Opposition frontbench, as part of frontbenchers to the parliament.

In most countries, a member of the shadow cabinet is referred to as a shadow minister. In the United Kingdom's House of Lords and in New Zealand, the term spokesperson is used instead of shadow. In Canada, the term opposition critic is also used.