Reformed confession of faith that is used by many of the Reformed churches. It was written in 1562 primarily by Caspar Olevianus, the superintendent of the Palatinate church, and Zacharias Ursinus, a professor of the theological faculty of the University of Heidelberg. It was accepted at the annual synod of the Palatinate church in 1563.

The Heidelberg Catechism was prepared as part of a reform program directed by Elector Frederick III the Pious, who was attempting to complete the religious reformation of the Palatinate. Although Frederick preferred the Reformed faith, he hoped to conciliate the contending Protestant groups, which included the orthodox Lutheran party ranged against both the Reformed party and the more moderate Lutheran followers of Philipp Melanchthon. The elector hoped that the Heidelberg Catechism would form the basis for reconciliation.

The authors of the Heidelberg Catechism based the work on earlier catechetical works by themselves and others, and they attempted to prepare a catechism acceptable to all. In discussing the sacraments, they sought to bring their Reformed statements as near to the moderate Melanchthonian–Lutheran position as they could. The controversial doctrine of predestination was very mildly stated. The strength and appeal of the catechism was the fact that it was a practical and devotional work, rather than an intellectual, dogmatic, or polemical one.

Although the Heidelberg Catechism failed to conciliate the Protestant groups in Germany, it was widely accepted and used. It has been translated into more than 25 languages.