St. Bernard of Clairvaux was a French monk born in 1090, known for founding the Cistercian order, which emphasized a return to a simpler, more austere monastic life. He became a prominent religious leader and played a significant role in the reform of monastic practices during the Middle Ages. Bernard was also influential in promoting the Second Crusade and wrote extensively on theology and spirituality. His works, including sermons and letters, focused on the love of God and the importance of faith, making him a key figure in medieval Christianity. He was canonized as a saint in 1174.