A ballot box is a temporarily sealed container, usually cuboid, with a narrow slot in the top sufficient to accept a ballot paper in an election but which prevents anyone from accessing the votes cast until the close of the voting period. It will usually be located in a polling station although in some coutries, notably Ireland, there may also be ballot boxes that are taken to people's homes where they would otherwise be unable to travel to the polling station. When very large ballot papers are used, there may be a feeder mechanism to assist in the deposit of the paper into the box.

Transparent ballot boxes may be used in order for people to be able to witness that the box is empty prior to the start of the election.

At the close of the election all boxes are taken to a single location for tallying ("The count") and the result declared.

Ballot boxes are in some jurisdictions obsolete, because of the increase in paperless electronic voting.

The word ballot derives from voting systems based upon the use of a small ball instead of a voting paper: see blackball.