Huldrych or Ulrich Zwingli (1 January 1484 – 11 October 1531) was a leader of the Reformation in Switzerland, born during a time of emerging Swiss patriotism and increasing criticism of the Swiss mercenary system. He attended the University of Vienna and the University of Basel, a scholarly center of Renaissance humanism. He continued his studies while he served as a pastor in Glarus and later in Einsiedeln, where he was influenced by the writings of Erasmus.

In 1519, Zwingli became the Leutpriester (people's priest) of the Grossmünster in Zürich where he began to preach ideas on reform of the Catholic Church. In his first public controversy in 1522, he attacked the custom of fasting during Lent. In his publications, he noted corruption in the ecclesiastical hierarchy, promoted clerical marriage, and attacked the use of images in places of worship. Among his most notable contributions to the Reformation was his expository preaching, starting in 1519, through the Gospel of Matthew, before eventually using Biblical exegesis to go through the entire New Testament, a radical departure from the Catholic mass. In 1525, he introduced a new communion liturgy to replace the Mass. He also clashed with the Anabaptists, which resulted in their persecution. Historians have debated whether or not he turned Zürich into a theocracy.

The Reformation spread to other parts of the Swiss Confederation, but several cantons resisted, preferring to remain Catholic. Zwingli formed an alliance of Reformed cantons which divided the Confederation along religious lines. In 1529, a war was averted at the last moment between the two sides. Meanwhile, Zwingli's ideas came to the attention of Martin Luther and other reformers. They met at the Marburg Colloquy and agreed on many points of doctrine, but they could not reach an accord on the doctrine of the Real Presence of Christ in the Eucharist.

In 1531, Zwingli's alliance applied an unsuccessful food blockade on the Catholic cantons. The cantons responded with an attack at a moment when Zürich was ill-prepared, and Zwingli died on the battlefield. His legacy lives on in the confessions, liturgy, and church orders of the Reformed churches of today.