Bernard of Clairvaux
1090 — 1153
A Cistercian abbot who reshaped medieval monastic life, Bernard of Clairvaux entered the monastery at Cîteaux in 1113 with thirty companions and two years later founded Clairvaux, which spawned 68 daughter houses in his lifetime. He advised popes, preached the Second Crusade, wrote 86 sermons on the Song of Songs, and shaped Marian devotion across the Western church. Dante placed him as his final guide in the Divine Comedy.