This thesis reasserts Alexander Henderson’s prominent place as the leading clerical spokesman for the Scottish Covenanters during the British Revolutions (1637-1646). Older biographies were hagiographical, portraying Henderson as a hero in the cause of liberty. Recent scholarly works on the Covenanter movement have often failed to do justice to its clerical leaders and their religious ideas. This thesis aims to correct both. Focusing on covenanting, preaching, ecclesiology and pamphleteering it reassesses Henderson’s public leadership especially in regard to the central role of religion. This thesis outlines Henderson’s various means of public communication, his self-fashioning as a leader, and how he was effective as a public figure in early modern Scotland. It begins with Alexander Henderson’s preparation for public service and his role as co-author of the National Covenant (1638), in which he popularized covenant theology as a political instrument focused on the issue of idolatry. It assesses Henderson’s preaching, in which he personalized the national struggles, and fused Scotland’s frustration over rule of Charles I with the popular hope for a blessed providential destiny. Henderson used a subtle but developing eschatology, providing Scotland with a greater sense of national identity. This is the first study to emphasise and to explore Henderson’s critical contribution to the Covenanter pamphleteering, as the most important author and/or editor of covenanter propaganda. Henderson led the movement in using pamphlets to argue for the duty of self-defence, and the obligations of ordinary men and women in early modern Scotland. Henderson developed an eschatological ecclesiology, raising presbyterian polity to a place of fundamental importance in the struggles with Charles I. This helped to provide the covenanters and Scotland with a greater sense of divine destiny, while also making it more difficult to forge a compromise at the Westminster Assembly.