(yōhän'əs brĕnz) , c.1522–67, German Protestant reformer. After coming under the influence of Johannes Oecolampadius and Martin Luther, Brenz stopped celebrating Mass (1523) and gave himself over to biblical exposition. He defended Luther's doctrine of the real presence of Jesus during the sacramentarian controversy (1525) in his Syngramma Suevicum. During the Schmalkaldic War (see Schmalkaldic League) he sought protection under Duke Ulrich of Württemberg, and became the leader of the Reformation in Württemberg.