Heinrich Bullinger (18 July 1504 – 17 September 1575) was a Swiss reformer, the successor of Huldrych Zwingli as head of the Zürich church and pastor at Grossmünster. As one of the most important reformers in the Swiss reformation, Bullinger is known for co-authoring the Helvetic Confessions and his work with John Calvin on the Real Presence of Christ in the Eucharist. Bullinger's importance in the Reformation has long been underestimated; recent research shows that he was one of the most influential theologians of the Protestant Reformation in the 16th century.