Forced to leave Italy because of his Protestant views, Girolamo Zanchi (1516-1590) became a respected Reformed theologian abroad and helped to shape the emerging 'Reformed Orthodoxy'. Zanchi's work on a common confession of faith for the Reformed churches placed him at the heart of the international Reformed community. Although that project was never brought to fruition, the result of Zanchi's efforts was De religione christiana fides, a critical edition of which is published here, alongside a 16th-century English translation of the work. De religione christiana fides serves as a compendium of Zanchi's mature theology and reflects the development of Reformed dogmatics and polemic more generally in the late 16th century. It therefore provides an interesting picture of the theology of a whole era.