Saint William (or Saint Guillaume) de Donjeon was born in 1140AD at the Castle of Arthel, near Nevers (a town in central modern day France). His father initially hoped his son would become a soldier, but Saint William chose a different path, choosing to instead be educated by his uncle (on his mother's side) Pierre who was at the time the Archdeacon of Soissons. After his education, Saint William became a canon, first in Soissons and then in Paris. Though the lifestyle initially made him content, he soon resolved to break apart from society and entered the Order of Grandmont. This order lived a strict and austere religious life, with it's founder Saint Stephen of Muret famously compiling the Rule of Saint Stephen - There is no rule save the Gospel of Christ.
Initially pleased with this new order, Saint William would eventually become troubled and disappointed by the many internal conflicts happening in the order and so on 1167 Saint William joined the Cistercians. He assumed the habit at Pontigny Abbey and in 1184 he became the abbot of Fontaine-Jean Abbey near Sens. He would later serve as the abbot of Chaalis Abbey from 1187 to 1200.
In 1200, the priests of Bourges gathered together and elected Saint William as the new Archbishop of Bourges, France. He met this election with an initial resolve not to accept but his order's general (the abbot of Citeaux) commanded him to accept followed by another prompt to accept from Pope Innocent III. As Archbishop, Saint William doubled his penances and austerities famously telling others that it was now incumbent on him to do penance for both himself and others. He would always have a hair-shirt under his habit, never ate meat, and would never add clothes during the winter or remove clothes during the summer. Saint William was famous for his ministering to the poor believing he was sent by God to care for them. Saint William had a deep devotion to the Blessed Sacrament, often spending hours at the foot of the Altar.
Saint William was instrumental in keeping the construction of the Cathedral of Saint Stephen going and was able to celebrate Christmas Mass in 1208 at the Cathedral. He was a staunch defender of clerical rights against the state, going so far as even having a public dispute with King Philip II when the King had been rebuked from Pope Innocent III over his divorce. In the latter stages of his life, Saint William worked diligently to combat and convert the Albigenses (a branch of the Cathartisic movement).
On January 9th, 1209, Saint William fell ill. Through the strength he had left, he kneeled at the altar and died shortly after midnight on the 10th. According to his last will and testament, Saint William was buried with his hair shirt and on top of ashes. Pope Honorius III formally canonized him a saint on May 17th, 1218 and his body was preserved with great veneration until 1562 when they were destroyed by the Huguenots. Many miracles were attested by bother Saint William and his relics.
Today his feast day is recorded for January 10th in the Roman Catholic Church and is the patron saint of the University of Paris.