Universal suffrage (or franchise) ensures the right to vote for as many people who are bound by a government's laws as possible, as supported by the "one person, one vote" principle. For many, the term universal suffrage assumes the exclusion of youth and non-citizens (among others), while some insist that much more inclusion is needed before suffrage can be called universal. Democratic theorists, especially those hoping to achieve more universal suffrage, support presumptive inclusion, where the legal system would protect the voting rights of all subjects unless the government can clearly prove that disenfranchisement is necessary.

While this article documents no examples of suffrage having been extended universally (by its most inclusive definition), healthy democracies have slowly expanded voting rights, including to some non-citizens and youth. However, democratic backsliding through voter suppression and election subversion threatens free and fair elections and weakens the power of the voting process. Autocratic governments even hold sham elections to try and pretend that they haven't fully revoked suffrage from their voters.