A faithless elector is a member of an electoral college who refuses to cast a vote for his or her pledged candidate. This term is used most commonly in American politics, although technically members of electoral colleges all over the world could be faithless electors, if they so desired. Faithless electors are often subject to political reprisal for their actions, in cases where they can be identified. In other areas, the ballots of the electors are secret, so it's possible to develop a list of suspects, but the identity of the faithless elector cannot be confirmed.

An electoral college is a group of individuals known as electors who are convened to elect a public official. Typically, the electors are given a mandate by the voters, with electors being “pledged” to vote for specific candidates or parties. Unpledged electors may vote for whomever they like. In the case of pledged electors, if the elector votes for someone other than his or her candidate, that person becomes a faithless elector.

In the history of the American electoral college, as of 2008 156 faithless electors had been recorded. Of these 156, 71 were forced to become faithless electors because their pledged candidates died between the general election and the convening of the electoral college. The others deliberately chose to cast votes for other candidates, for a variety of reasons, although a few appear to have been faithless by accident, as in 2004 when a faithless elector in Minnesota accidentally wrote “John Edwards” on both the Presidential and Vice-Presidential ballots.

Several faithless electors have made a conscious decision to vote for the opposition candidate because they feel that the candidate is better suited to the job. In other instances, an elector may defect as a political statement. Some electors from Washington, DC, for example, have chosen to cast blank ballots to protest the region's lack of statehood and representation in the federal government. Other faithless electors have also defied their pledges to protest what they perceive as stolen or questionable elections.

In some regions, there are specific laws which provide penalties for someone who chooses to become a faithless elector. Others may be subject to Party censure and public disapproval, but face no legal penalties. Because of the risk of defection, electors are usually chosen very carefully. High-ranking and especially loyal members of political parties are the best candidates for positions as electors, since they are the least likely to violate their pledge.