The Waldensians, also known as Waldenses (), Vallenses, Valdesi, or Vaudois, are adherents of a church tradition that began as an ascetic movement within Western Christianity before the Reformation. Originally known as the Poor of Lyon in the late 12th century, the movement spread to the Cottian Alps in what is today France and Italy. The founding of the Waldensians is attributed to Peter Waldo, a wealthy merchant who gave away his property around 1173, preaching apostolic poverty as the way to perfection.
In some aspects the Waldensians of the Middle Ages could be seen as proto-Protestants, but they mostly did not raise the doctrinal objections characteristic of sixteenth-century Protestant leaders. They came to align themselves with Protestantism: with the Resolutions of Chanforan [fr] on 12 September 1532, they formally became a part of the Calvinist tradition. They were nearly annihilated in the seventeenth century.