The religious thought of the nineteenth century is often associated with heterodoxy, skepticism, and the radical criticism occasioned by the work of Darwin, Marx, Nietzsche, and later Freud. While these movements and thinkers were significant, we should not view the period merely in terms of a steady march toward atheism and secularity. The long nineteenth century can be considered one of the most diverse and fruitful periods for theological work with the immense profusion of thought forms, intellectual challenges, and innovative developments that were generated in Europe. Often breaking out in new directions, the leading thinkers of the period also wrestled with the challenges of the eighteenth-century Enlightenment; these include questions surrounding the rational basis for religious belief, the historical reliability of sacred texts, and the foundation of ethics. In this chapter, much of the focus is on a succession of seminal thinkers, many of whom flourished in the universities of Germany under conditions that fostered academic rigor and facilitated an emerging if hard-won intellectual freedom. Particular attention is given to the impact of historical work, strategies that mediated between Christian doctrine and modernity, the reinvigoration of confessional theologies, and the influence of politics, natural science, and the empirical study of religion. The following selection is thematic rather than chronological.