In electoral politics, a third party is any party contending for votes that failed to outpoll either of its two strongest rivals (or, in the context of an impending election, is considered highly unlikely to do so). The distinction is particularly significant in  two-party systems. In any case "third" is often used figuratively, as in "the third parties", where the intent, literally stated, is "the third and succeeding parties".

The term third party is used in the United States for any and all political parties in the United States other than one of the two major parties (Republican Party and Democratic Party). The term can also refer to independent politicians not affiliated with any party at all and to write-in candidates.