Johannes Oecolampadius (pronounced ök?lämpä`d?oos or ?k'àl?mp?`d?às) (1482–1531), a German Protestant reformer, associate of Huldreich Zwingli in the Reformation in Switzerland. He was in 1516 a preacher at Basel, where he worked with Erasmus on his New Testament. In 1520 he preached in Augsburg, then for a time was in a convent at Altmünster. Martin Luther's teachings won his interest, and in 1522 he acted as chaplain among reformers under Franz von Sickingen at Ebernburg and then returned to Basel to devote himself to the work of the Reformation. He agreed with the views of Zwingli on the nature of the Eucharist, defending this position against Luther in the Colloquy of Marburg, 1529, while Zwingli disputed the question with Melanchthon.