Reformed church that developed in Hungary during and after the 16th-century Protestant Reformation. The influence of the Reformation was felt early in Hungary. A synod at Erdod adopted the Lutheran Augsburg Confession in 1545, and by 1567 the Synod of Debrecen adopted the Reformed Heidelberg Catechism and the Second Helvetic Confession.

Except for minor reverses, the Protestants made progress in Hungary for many years. The Roman Catholic Counter-Reformation, however, began in the 17th century, and most Hungarian nobles were reconverted to Roman Catholicism by mid-century. The Protestants suffered persecutions and difficulties until 1781, when Joseph II, the Holy Roman emperor, promulgated the Edict of Toleration, which granted religious liberty to the Protestants.

The Magyars (Hungarians (Hungarian)) spread rather widely through the Holy Roman Empire, taking their Reformed faith with them. Within the empire they built up a large system of schools, elementary through university, and did much for Hungarian cultural life.

The Treaty of Versailles (Versailles, Treaty of) (1919) following World War I shattered the Hungarian Reformed Church. Only half of the church remained within the new Hungary. The other half was represented by minority groups in countries that were unfriendly or even hostile to them. The largest segment, in Romania, suffered considerably for both religious and cultural reasons. As the country became more stable, however, the church regained its strength.

For many years after the Treaty of Versailles, the Magyar people, split between Hungary, Romania, and other countries, had hoped that eventually they would be reunited in one political unit and that their church would also be reunited. All hope of reunion was lost after World War II. When the communists gained power in Hungary in 1948, the Reformed Church did not resist the new government and submitted to its restrictions.

In the early 1990s, with the collapse of the communist government in Hungary, the Reformed Church began to reopen some of its seminaries and churches. It also sought closer ties with Reformed and Presbyterian churches in other parts of Europe and in North America. The church claims almost two million members and is the second-largest religious body in Hungary.