Abstention is a term in election procedure for when a participant in a vote either does not go to vote (on election day) or, in parliamentary procedure, is present during the vote but does not cast a ballot. Abstention must be contrasted with "blank vote", in which a voter casts a ballot willfully made invalid by marking it wrongly or by not marking anything at all. A "blank voter" has voted, although their vote may be considered a spoilt vote, depending on each legislation, while an abstaining voter has not voted. Both forms (abstention and blank vote) may or may not, depending on the circumstances, be considered to be a protest vote (also known as a "blank vote"). Abstention is related to political apathy and low voter turnout.

An abstention may be used to indicate the voting individual's ambivalence about the measure, or mild disapproval that does not rise to the level of active opposition. Abstention can also be used when someone has a certain position about an issue, but since the popular sentiment supports the opposite, it might not be politically expedient to vote according to their conscience. A person may also abstain when they do not feel adequately informed about the issue at hand, or have not participated in relevant discussion. In parliamentary procedure, a member may be required to abstain in the case of a real or perceived conflict of interest.

Abstentions do not count in tallying the vote negatively or positively; when members abstain, they are in effect attending only to contribute to a quorum. Instead, blank votes may be counted in the total of votes, depending on the legislation.

An active abstention can occur when a voter votes in a way that balances out their vote as if they had never voted. This has occurred many times in the House of Commons of the United Kingdom. During a division (a process where a yes/no vote occurs to agree or disagree with a motion), a Member of Parliament may actively abstain by voting both "yes" and "no". This is effectively the same as not voting at all, as the outcome will not be changed by active abstention. However, in the House of Lords of the United Kingdom, active abstention is not possible as a Lord voting both ways will be removed from the list of votes.

In another manner, an intentionally spoilt vote could be interpreted as an active abstention. Because of the nature of an abstention, only intentionally spoiled ballots could be counted as active abstention.^{[citation needed]}

In the United Nations Security Council, representatives of the five countries holding a veto power (the United States, United Kingdom, France, Russia and China) sometimes abstain rather than vetoing a measure about which they are less than enthusiastic, particularly if the measure otherwise has broad support. By convention, their abstention does not block the measure.^{[citation needed]} If a majority of members of the United Nations General Assembly or one of its committees abstain on a measure, then the measure fails.

In the Council of the European Union, an abstention on a matter decided by unanimity has the effect of a yes vote; on matters decided by qualified majority it has an effect of a no vote.

In the Italian Senate, an abstention used to have the effects of a no vote. This was changed in 2017, when it was established that a measure only needed for the number of yes votes to be higher than the number of no votes in order to pass, with abstentions being counted neither as yes votes nor as no votes.