The French religious leader Peter Waldo (died ca. 1218) believed in voluntary poverty and religious simplicity. His followers were considered heretics by the Church.

Some men's personal lives are eclipsed by the movements they start. Peter Waldo was such a man. He appears on the scene of history in 1170 in Lyons as a successful businessman who, touched to his core by a traveling minstrel's religious ballad, gave away his money to live in poverty as a preacher of the Gospel. Having persuaded a sympathetic priest to translate large sections of the New Testament from Latin into the regional language, Provençal, Peter wandered through Lyons, bringing the message of Christ to anyone who would listen to him. He soon had the Gospels memorized. A number of young men, impressed by his intelligence and sincerity, followed him in giving away their possessions and found a new joy and freedom in living according to the spirit of the Gospels.

Some priests of Lyons, disturbed by Peter's popularity, tried to curb his activities. Peter appealed directly to Pope Alexander III in Rome. The Pope responded in 1179 by praising the group's poverty but said that because they had no theological training they could preach only if the archbishop of Lyons gave them permission. The Waldenses, as they had come to be known, felt that their message was too important to be checked by traditional Church discipline, and they rejected the Pope's directive. They were excommunicated at a Church council in Verona by the next pope, Lucius III, in 1184.

The Waldenses continued to live by their understanding of the New Testament rather than by the teachings of the Church. They refused to accept the existence of purgatory because it is not in the Bible. They rejected the practice of venerating the saints for the same reason. Not just priests, they said, but any person can consecrate the sacramental bread and wine. They rejected the authority structure of the Church as unbiblical. Their refusal to take oaths and also to participate in war made them unpopular with the secular as well as the Church authorities. Peter Waldo himself was not heard from after his excommunication in 1184. His followers were harassed by the Inquisition. They escaped when possible to the nearly inaccessible mountain regions of northern Italy, where Waldo's ideas managed to survive over the centuries despite periodic attempts by Church authorities to eliminate them.