This is the first book to examine one of Europe's largest Protestant communities in Hungary and Transylvania. It highlights the place of the Hungarian Reformed church in the international Calvinist world, and reveals the impact of Calvinism on Hungarian politics and society. Calvinism attracted strong support in Hungary and Transylvania, where one of the largest Reformed churches was established by the early seventeenth century. Understanding of this Hungarian Reformed church remains the most significant missing element in the analysis of European Calvinism. The Hungarian Reformed church survived on narrow ground between the Habsburgs and Turks, thanks to support from Transylvanias princes and local nobles. They worked with Reformed clergy to maintain contact with western co-religionists, to combat confessional rivals, to improve standards of education and to impose moral discipline. However, there were also tensions within the church over further reforms of public worship and church government, and over the impact of puritanism. This book examines the development of the Hungarian church within the international Calvinist community, and the impact of Calvinism on Hungarian politics and society.