Bernard of Clairvaux, O.Cist (1090--August 20, 1153) was a French abbot and the primary builder of the reforming Cistercian order.
After the death of his mother, Bernard sought admission into the Cistercian order. Three years later, he was sent to found a new abbey at an isolated clearing in a glen known as the Val d'Absinthe, about 15 km southeast of Bar-sur-Aube. According to tradition, Bernard founded the monastery on 25 June 1115, naming it Claire Vallée, which evolved into Clairvaux. There Bernard would preach an immediate faith, in which the intercessor was the Virgin Mary. In the year 1128, Bernard assisted at the Council of Troyes, at which he traced the outlines of the Rule of the Knights Templar, who soon became the ideal of Christian nobility.
Bernard died at age 63, after 40 years spent in the cloister. He was the first Cistercian monk placed on the calendar of saints, and was canonized by Pope Alexander III on 18 January 1174. Pope Pius VIII bestowed upon him the title "Doctor of the Church".