The political potential of millenarian religion has long exercised the interests of scholars of western history and religion. The religious vision of an imminent messianic age in modernity was once commonly contrasted with secular movements for revolutionary change such as socialism. Recent shifts in historiography and the study of religion have downplayed such comparisons, and yet early industrial England witnessed significant interactions between millenarianism and traditions of radical popular politics, including the first English socialisms. This book offers a new explanation of such interactions, revealing their basis in rich traditions of popular theology and religious practice, and not the collective disillusion and secular conversions once thought. Through a detailed archive-based study of the popular millenarian movement of Southcottianism - the followers of Joanna Southcott - from 1815 to 1840, this work challenges social and gender views of plebeian religion in the period. Adopting innovative approaches in the history of religion, including a view of theology from the perspective of millenarians themselves, this book further overturns existing assumptions about millenarian attitudes to agency, including those of E.P. Thompson's The Making of the English Working Class. This history of Southcottianism provides a compelling case-study of the political possibilities of visionary religion, revealing how theology framed popular conceptions of human and divine agency in the making of the millennium, and was intimately involved in an early collaboration between the competing Christian and secular visions of transformation which have shaped the modern world.