In a first-past-the-post electoral system (FPTP or FPP), formally called single-member plurality voting (SMP) when used in single-member districts or informally choose-one voting in contrast to ranked voting, or score voting, voters cast their vote for a candidate of their choice, and the candidate who receives the most votes wins even if the top candidate gets less than 50%, which can happen when there are more than two popular candidates.

As a winner-take-all method, FPTP often produces disproportional results, particularly when electing members of an assembly (such as a parliament) in the sense that political parties do not get representation according to their share of the popular vote. This usually favours the largest party and parties with strong regional support to the detriment of smaller parties without a geographically concentrated base. Supporters of electoral reform are generally highly critical of FPTP because of this and point out other flaws, such as FPTP's vulnerability to gerrymandering, the high amount of wasted votes and the chance of a majority reversal (when the party that wins the most votes gets fewer seats than the second largest party, and so loses the election). Throughout the 20th century many countries that previously used FPTP abandoned it in favour of other electoral systems, but FPTP is still used as the primary form of allocating seats for legislative elections in about a third of the world's countries, mostly in the English-speaking world.

Some countries use FPTP alongside proportional representation in a parallel voting system, the PR element not compensating for but added to the disproportionality of FPTP. Others use it in so-called compensatory mixed systems, such as part of mixed-member proportional representation or mixed single vote systems, which aim to counterbalance these. In some countries that elect their legislatures by proportional representation, FPTP is used to elect their head of state.