A write-in candidate is a candidate whose name does not appear on the ballot but seeks election by asking voters to cast a vote for the candidate by physically writing in the person's name on the ballot. Depending on electoral law it may be possible to win an election by winning a sufficient number of such write-in votes, which count equally as if the person was formally listed on the ballot.

Writing in a name that is not already on the election ballot is considered a practice of the United States. However, some other jurisdictions have allowed this practice. In the United States, there are variations in laws governing write-in candidates, depending on the office (federal or local) and whether the election is a primary election or the general election; general practice is an empty field close by annotated to explain its purpose on the ballot if it applies. In five U.S. states there are no elections to which it can apply, under their present laws. Election laws are enacted by each state and in the District of Columbia, to apply to their voters.