Heinrich Bullinger (18 July 1504 – 17 September 1575) was a Swiss reformer, the successor of Huldrych Zwingli as head of the Zurich church and pastor at Grossmünster. A much less controversial figure than John Calvin or Martin Luther, his importance has long been underestimated; recent research shows that he was one of the most influential theologians of the Protestant Reformation in the 16th century.