This book examines the transformation of elective monarchy in Transylvania and the Polish-Lithuanian Commonwealth in the 1570s. It does so by focusing on the foundational and experimental character of the first elections of 1571 (Transylvania) and 1573 and 1575–6 (Poland-Lithuania). In this period, the two polities adopted constitutions based on the same fundamental principles: elective thrones, state-sanctioned religious pluralism, and legal guarantees for the right of disobedience.