Peter Waldo
Peter Waldo (c.1140 - c.1205) was a wealthy French merchant from Lyon in the 12th century who became inspired to sell all that he had and begin preaching the Gospel, as the Apostles had done.
In 1173 at a spring festival, he heard a song about saint Alexius of Edessa, who had given up a large inheritance and a beautiful bride in order to live in poverty like Jesus. Hearing this, Waldo committed himself to studying the Bible and the writings of the Church Fathers. Eventually he decided to sell his home and his business to begin traveling around Lombardy preaching about the value of poverty. He quickly gained a following of people calling themselves the "Waldensians" and was asked to meet with Pope Alexander III. Having pleaded the case for their asceticism, they were laughed out of court.
Many of the Pope's clerics believed that the Waldensians were too poor to be allowed to preach. "Should pearls of wisdom be cast before swine?" - Walter Map, sent on a mission to the Pope's court by the English King, had asked. The Waldensians did not submit to this verdict, and denounced the pride and the corruption of clergy.
It is this anti-Roman zeal that has caused the medieval Waldensians to be labelled pre-protestant.
Modern Waldensians consider Waldo to be one of the most influential post-Nicene theologians, along with John Calvin.