Peter Waldo or Valdo or Pierre de Vaux (died 1218) was the founder of a radical ascetic Christian movement in 12th-century France.
Specific details of his life are largely unknown. It is believed that he was a rich merchant in Lyon making his money by "wicked usury", when around 1160 he was transformed into a radical Christian and gave his real estate to his wife, and the remainder of his belongings he distributed as alms to the poor.
Waldo also began to preach and teach on the streets, based on his ideas of simplicity and poverty notably that "No man can serve two masters, God and mammon." By 1170 he had gathered a number of followers and they came to be called The poor men of Lyon, the poor of Lombardy, or the Poor. They were also referred to as the Waldensians (or Waldenses).
They were distinct from the Albigensians and Cathars.
The Catholic church branded followers of Waldo's ideas heretics and strongly persecuted them, many were massacred in various European countries during the 12th and 13th centuries.
The Waldensian movement is characterised by lay preaching, voluntary poverty and a life of good works.
Most followers were absorbed into the new Protestant churches at the time of the Reformation. They maintain their separate identity in the valley of the Pellice River in Piedmont, an Alpine region of what is now Northern Italy.
In the 1970s the Italian Waldensians, organized in the Waldensian Evangelical Church, joined the Methodists to form the Union of Waldensian and Methodist Churches.