A motion or vote of no confidence (or the inverse, a motion or vote of confidence) is a motion and corresponding vote thereon in a deliberative assembly (usually a legislative body) as to whether an officer (typically an executive) is deemed fit to continue to occupy their office. The no-confidence vote is a defining constitutional element of a parliamentary system, in which the government's/executive's mandate rests upon the continued support (or at least non-opposition) of the majority in the legislature. Systems differ in whether such a motion may be directed against the prime minister, against the government (this could be a majority government or a minority government/coalition government), against individual cabinet ministers, against the cabinet as a whole, or some combination of the above.

A censure motion is different from a no-confidence motion. In a parliamentary system, a vote of no confidence leads to the resignation of the prime minister and cabinet, or, depending on the constitutional procedure at hand, a snap election to potentially replace the government.

A vote in favour of censure is a non-constitutionally-binding expression of disapproval; a motion of censure may be against an individual minister or a group of ministers. Depending on a country's constitution, a no-confidence motion may be directed against the entire cabinet. Depending on the applicable rules, a mover of a censure motion may need to state the reasons for the motion, but specific reasons may not be required for no-confidence motions. However, in some countries, especially those with uncodified constitutions, what constitutes a no-confidence vote sufficient to force the resignation of high officeholders may not be clear. Even if the government is not constitutionally bound to resign after losing a given vote, such a result may be taken as an ominous sign for the government and may prompt its resignation or the calling of a snap election.

In addition to explicit motions of confidence and no-confidence, some bills (almost always the government budget and sometimes other key pieces of legislation) may be declared to be a confidence vote – that is, the vote on the bill is treated as a question of confidence in the government; a defeat of the bill expresses no confidence in the government and may cause the resignation of the prime minister and cabinet or the calling of an election.

There are a number of variations in this procedure between parliaments. In some countries, a motion of no confidence can be directed at the government collectively or at any individual member, including the prime minister. Sometimes, motions of confidence or no confidence are proposed even though it is clear that the government does in fact have majority support simply to pressure ministers or put opposition parties in the potentially embarrassing situation of voting in support of the government.

In many parliamentary democracies, there are limits to how often a confidence vote may be held, such as being allowed only once every three or six months. Thus, the timing of a motion of no confidence is a matter of political judgment. A motion of no confidence on a relatively trivial matter may then prove counterproductive if an issue suddenly arises that is seen to be a more credible justification for a motion of no confidence.

Sometimes, the government chooses to declare that one of its bills is a "vote of confidence" to prevent dissident members of its own party from voting against it. However, this is a political risk, especially when the Prime Minister's majority is not assured, such as if the ruling party/coalition is internally divided, or in minority government; if the bill fails (and thus it is shown that parliament has lost its confidence in the government), the Prime Minister is expected to resign or call snap elections. In Westminster systems, the government budget is always a vote of confidence; even a successful amendment to the budget may be considered a no-confidence vote.

It is not necessarily the case that a vote with the effect of a motion of no confidence be introduced as such. As stated above, certain pieces of legislation may be treated as confidence issues. In some cases, the motion may be an ordinary legislative or procedural matter of little substantive importance used for the purpose of testing the government's majority, such as the 1895 vote of no confidence in the Earl of Rosebery's government, which was technically a motion to reduce the salary of a minister by a nominal sum.