The secret ballot, also known as the Australian ballot, is a voting method in which a voter's identity in an election or a referendum is anonymous. This forestalls attempts to influence the voter by intimidation, blackmailing, and potential vote buying. This system is one means of achieving the goal of political privacy.

Secret ballots are used in conjunction with various voting systems. The most basic form of a secret ballot utilizes blank pieces of paper upon which each voter writes their choice. Without revealing the votes to anyone, the voter folds the ballot paper in half and places it in a sealed box. This box is later emptied for counting. An aspect of secret voting is the provision of a voting booth to enable the voter to write on the ballot paper without others being able to see what is being written. Today, printed ballot papers are usually provided, with the names of the candidates or questions and respective check boxes. Provisions are made at the polling place for the voters to record their preferences in secret, and the ballots are designed to eliminate bias and to prevent anyone from linking voter to ballot.

A privacy problem arises with moves to improve efficiency of voting by the introduction of postal voting and remote electronic voting. Some countries permit proxy voting, but some people argue that this is inconsistent with voting privacy. Popularity of the ballot selfie has challenged the secrecy of in-person voting.