Petrus Waldus was a 12th-century merchant from Lyon, France, who became known for his involvement in the Waldensian movement. The movement, which was named after him, emphasized the importance of preaching and living a simple, humble Christian life. Waldus and his followers were known for their commitment to poverty, preaching, and the translation of the Bible into the vernacular language. Their beliefs and practices led to conflicts with the established church, but the movement continued to have an impact on the Protestant Reformation and the development of Christian thought.