Plurality voting is an electoral system in which the candidates in an electoral district who poll more than any other (that is, receive a plurality or relative majority) are elected.

Under single-winner plurality voting, and in systems based on single-member districts, plurality voting is called single member [district] plurality (SMP), which is occasionally known as "first-past-the-post". In plurality voting the leading candidate, whether or not they have a majority of votes, is elected. Under all but a few niche election systems, the most-popular are elected. But under systems that use ranked votes, vote tallies change and are compared at various times during the vote count process. Where votes are transferred, the system is not generally referred to as a plurality system.

There are several versions of plurality voting for multi-member district. The system that elects multiple winners at once with the plurality rule and where each voter casts as many X votes as the number of seats in a multi-seat district is referred to as plurality block voting. A semi-proportional system that elects multiple winners elected at once with the plurality rule and where each voter casts more than one vote but fewer than the number of seats to fill in a multi-seat district is known as limited voting. A semi-proportional system that elects multiple winners elected at once with the plurality rule and where each voter casts just one vote in a multi-seat district is known as single non-transferable voting.

Plurality voting is widely used throughout the English-speaking world as a result of its spread by the British Empire, including in most of the United States. Outside of the English-speaking world, it is less popular^{[citation needed]} than its close relatives in the runoff family of methods. Overall, more countries in the world use a form of proportional representation than use plurality or a form of runoff.

In single-winner plurality voting, each voter is allowed to vote for only one candidate, and the winner of the election is the candidate who represents a plurality of voters or, in other words, received more votes than any other candidate. In an election for a single seat, such as for president in a presidential system, voters may vote for one candidate from a list of the candidates who are competing, and the winner is whichever candidate receives the highest number of votes. Compare plurality voting to a majority system, the two-round system, where usually the top two candidates in the first ballot progress to the second round, also called the runoff. A runoff is by default not held, if a candidate already received an absolute majority in the first ballot (more than half of votes), and in the second ballot, where there are only two candidates, one of the candidates will (except for a tie) receive a majority. Under plurality rules, the candidates are not at any point in the election required to have majority support.

In an election for a legislative body with single-member seats, each voter in a geographically defined electoral district may vote for one candidate from a list of the candidates who are competing to represent that district. Under the plurality system, the winner of the election then becomes the representative of the whole electoral district and serves with representatives of other electoral districts. That makes plurality voting among the simplest of all electoral systems for voters and vote counting officials; however, the drawing of district boundary lines can be contentious in the plurality system (see gerrymandering). The system is also independent of parties; the party with the most votes overall may not win the most seats overall (electoral inversion). Note that issues arising from single-member districts are still in place with majority voting systems, like the two-round system and instant-runoff voting too.

The same principle used in single-winner plurality voting (electing the candidate with the most votes) is also used in approval voting, however with very different effects, as voters can choose to support as many or few candidates as they choose, not just one. For this reason, approval voting is usually distinguished from plurality voting, while technically being a sub-type of it.

Multi-member plurality elections are only slightly more complicated. Where n is the number of seats in the district, the n candidates who get more votes than the others are elected; the winners are the n candidates with the largest number of votes. The rules may allow the voter to vote for one candidate, for a number of candidates more than one but less than n, for as many as n candidates, or some other number.